Not sure if this is the appropriate area, but I'm not sure this bike counts as vintage... (I'm guessing mid-90's or later)

Anyway, bought a cheap commuter bike. Had been really poorly repainted and converted to singlespeed. Is a mishmash of parts, 60's TTT stem, SR Sakae post and cranks, selle italia saddle, dia compe sidepull front brake, exage wheels. The frame is aluminum (as are dropouts, bottom bracket, etc.) and has some odd frame features. The guy I bought it didn't paint it (a prior owner did) and he didn't know what brand it was. Seems to have been red before (inside of brake bolt hole), but even though the paint is terrible, looks like whomever did it stripped it, so there isn't much .

Rides fine, a bit harsh, but it fits me nicely, so it'll be fine for awhile to beat up on.

On the outside of the BB, it has a presumed s/n F9099905 - I looked at all the major brands and that doesn't seem to make sense for any of them (Trek/Schwinn/Fuji/etc., etc.). No markings anywhere else except 3K 049 on the BB, which is the BB size, I believe.

The odd and distinctive frame features are the integrated seat stays/seat clamp bolt, which is way bigger than on the trek aluminum bikes (also, no cut in back, like on some older steel bikes I've had). It also has a square rear brake bolt hole. The dropouts are distinctive, too. I've spent several hours looking through serial number sets and looking for those distinctive features on aluminum bike pictures and have come up empty.

I thought it'd be easy to figure out what it was. It wasn't.

(Pictures attached)

Any thoughts?

Thanks,
Eric