A tire was my guess, maybe a 30028?
I’m surprised you don’t have 3956s. From the Lego I had as a kid, I had several of those but none of the other brackets (like 44728, 99207, and 99781).
I am currently compiling a list of parts used in various Intercept Orbit and Rapid Attack instructions I found so I can go shopping on BrickLink. It’s a slow process, but I’d be willing to share here when I’m done.
Okay, I’ve done the 6 ships in the MFZ: Intercept Orbit book. Even if I don’t build these ships, it was a useful exercise to see what sort of pieces are common in MFZ builds.
I have a large number of MFZ: Rapid Attack builds still to go through.
Oh my stars that looks like it was a LOT of work! But amazing, thank you so much!
I had to order some 2x2x2 L pieces because they’re just so common in the next build, so I’m waiting for those to show up before I tackle the next ship.
Well @Marx, it seems you’ve gotten me back into building micro scale LEGO spaceships. Here are a few designs I slapped together this afternoon when I got sick of watching Netflix.
Y’all are making me seriously regret giving my entire lego collection to my nieces/nephew.
I was inspired by this thread to get try out one of the COBI World War II sets and ordered the IJN Musashi. It will be a hair under 3 feet long when assembled and if I like it, I will probably get their USS Missouri set to even things out.
(NB: It’s not Mobile Frame related, so I’ll post the finished pics in my watch thread as a whimsical diversion.) 
(NB2: I see now that I was photo-bombed by Jabba the Hutt. That guy is such a ham.)
How is the quality of the COBI blocks? I’d love to get a model like that, but the poor fitting of non lego products in the past has made me leery.
We shall soon see. I have not heard anything bad about them though. They also have a marketing tie-in with World of Warships now, so I’m guessing it will be fine.
Feel free to post the pictures here, if you’d like! This was primarily MFZ:IO, but I don’t think it’s “busy” enough to not be a catch-all for LEGO (and plastic brick building) stuff in general!
How much did the kit cost? I saw a 3rd-party kit for a Babylon 5 Earthgov Destroyer that I almost pulled the trigger on, but quality fears kept me from doing so.
It cost too much ($180.00US), but that’s way less than many “collectible” LEGO Star Wars sets. Regardless, I will let you all know what I think about these COBI World War II sets once I’ve assembled this one.
NB: My Sweetheart told me that she would be amenable to building this with me on Wednesday! So…this will have to wait until then! 
Well, I’ve opened the box and…holy moly. Lots of stuff. And yes; the instructions are in two (not insubstantial) volumes. 
Update: First packet done. Quality is good, as is the fit, so far anyway. It’s taking shape. (I haven’t skipped ahead to look, but I am confident that this is the aft section of the hull)
Update (June 6, 2020; D-Day +76 years): Second and third packets assembled. It is the aft hull and the spotter plane deck and tracking, as well as the rudder, screws, and skegs are in place. To answer @Sagantine’s question, quality so far has been excellent. This thing is STURDY. I’m pleased so far.
Update: Sorry, but real life has interrupted my building, and I am no further along than the last post. Hopefully, I can get more done this weekend.
The FTL Lanius cruiser above was extremely fragile, so I disassembled it and built a Rock cruiser instead:
FTL ships! Amazing!
My favourite aesthetic design was probably the Engi designs, although the Zoltan Cruisers were pretty cool too.
I was going to make the Zoltan next. I should have enough pieces, the question is whether I can get a reasonable color scheme with what I’ve got left.
Bought a new LEGO Creator set which I had a bunch of fun with.
I’ll probably break it all down before long and transform it into more MFZ:IO models before long, but for now it’s pretty cool:
I always admire the way that the creative minds at LEGO work. Those little touches on the inside… damn impressive (a little potted plant, a coffee cup, a water spout…).
Makes me miss being a kid and just playing with the LEGO for hours on my own after assembling it. Oh well. Someday.
Believe it or not, my last post here in June was the last time I did any work on the Musashi model! Real life has been hectic. Anyway, this weekend I actually took everything out and made a concerted effort to at least get the hull completed. It’s looking good:
I will say this about COBI: the manufacturing quality is excellent, and the plastic seems to be more durable than actual LEGO (but not as solid as older 1970s-1980s era LEGO pieces, which were well-nigh indestructible). The instructions are good, but do not make a strong enough distinction between gray and tan, thus causing me to study the diagrams a bit more than I want to. It’s okay when both gray and tan pieces are represented on the same page, but for just gray pieces it’s proven problematic for me. A comparison of the directions in the first photo gives an idea, although the distinction in real life is not nearly so obvious as in the photo. Also, there are angled pieces of different depth that are just way too similar-looking in the diagrams, and I have had to backtrack and disassemble components to swap them out more than once. Those are minor annoyances, however, and I’m rather pleased with my purchase so far.
Encouraged by Boydesian, and with this last weekend off before the holiday ©rush hits, I decided to make one more LEGO spaceship for Mobile Frame Zero: IO before I won’t have time for anything besides Work, Other Work, and School:
No side-wings (that somehow are supposed to attach to the engines of this design) because it requires 2 hexagonal attachment pieces and I only have one… oh well. I still think it looks pretty cool.
Also, way easier to build ships now that I have my collection organized by shape/size/function.
