robbyville Thanks for providing photos.

It appears that the aluminum protrusion both front and rear is ever so slightly too thick making them not want to slide into neither the front, nor the rear dropouts. This is interesting. Now might be a good time to get that metric digital dial caliper and take some measurements, comparing with opening width between the parallel faces of the front and rear drops on both the Speedvagen and the DeRosa SLX (in units of, say 0.01mm or .001” take your pick). You could gain a wee bit of rear dropout clearance on the rear dropouts just by scraping the remaining paint away & down to the chrome plating that remains.

For the front wheel, Just by looking, it really appears as if the “protrusion” part of the aluminum axle is too thick to clear the thick chrome plating of your DeRosa fork ends. If it were me I would consider filing the chrome off of the notch in the forkends for a minute, but then stop myself. It would be less destructive and almost as easy to disassemble the front axle and chuck the aluminum axle in a drill press or metal lathe chuck and grind a tiny bit of material using a carbide cutter or grindstone. If you you tell Industry 9 about the issue and tell them precisely how far out of tolerance the “protrusions” are for your application, they may then direct you to send them in to them and they can make the modifications on a metal lathe or perhaps send you an alternate axle set that will be plug-n-play for you.

it would be a shame to not get those Industry 9’s to work great with your DeRosa.