Despite our spat the other day, we seem to me more alike than different. My tendency to build bikes that can't go faster than 30 mph is partly due to a bad right hand that seems to have a mind of it's own. Similar to the third leg taking over at times.
And now you are running front hub pretty fast too, which I did. I was happy enough with cornering the front hub bike untill I just got so much power on it that it spun the tire when you got back on the throttle even at speed. For me, that was at about 24s voltage, and when I went to 26s I started either crashing it or coming so close to it it scared me stupid. So you are getting real close now to what I consider the upper limits of safe riding with front hub in terms of power. Cruising at 35 mph should be safe enough if you have really good torque arms, and better than just hose clamps attaching them. I welded tabs to my forks to bolt on the torque arms.
That race bike was a very lateraly stiff old chromo mtb, so it did corner real nice. But off track, doing test runs on the street, there were enough potholes and just funky bumps in pavement to terrify me. I did break spokes one time. Above 40 mph, it simply was a real problem to hit a large bump like a patched hole where a trench had been run across a road for a gas or water line to a house.
A cheap FS wallbike, cannot corner as well due to both lateral frame flex, and flex of the cheap swingarms. So if you need suspension, it must be decent stuff.
My favorite bike at the moment is not so great, but has nice steel rear swingarms for attaching a motor. It's the mongoose blackcomb. For casual street riding below 30 mph, and moderately hard trail riding this bike is serving me very well. But the frame is laterally weak, and I immediately tossed the idea of racing it. So this bike would be ok for cruising 35 mph, but not cornering 35. Corners at 20 mph fine.
My best FS frame for lateral stiffness is an old 2005 Giant DS 3. This was a low end of the price range DH bike in it's day, so it had a somewhat heavy, but very strong frame. It has great lateral stiffness, but not as much as a good cromo frame. This is what you should look for I think. Something in a true DH frame. But not so high up the price range that it's going to shave too much weight. Not so new that it has more radical frame geometry designed solely for hucking huge drops either.
Though I haven't ridden one, an example of this kind of bike I was wanting to get, is the Kona Dawg. Of course, I liked the name too. These are going to be all alloy of course, so what you need to look for is beefy looking frames and swingarms, and particularly good rear dropouts that make designing your torque plates easier. Not lacy looking rear drops full of lightening holes.
Goes without saying, your next really fast bike ought to be rear hub. It could be a hardtail, if you streets are pretty nice in general where you live. They aren't here, except the brand new neighborhoods.