Update after 127 miles on rollers.
First off, a big thank you to Larry for suggesting the frame. The frame pretty much eliminates the problem of falling off. When a wheel slips off the bike stops and it's a non-issue. The only time I've fallen since the frame was when I tried to ride clipped in on the third day. The front wheel slipped off and I was not able to unclip my left foot fast enough and down I went. I may eventually clip in again but for now I am riding with platform pedals.
Here is the frame and bike
I found through trial and error that the front roller needs to be almost right under the axle. I originally had it about 2" further to the left. When pedaling the bike rocks slightly forward and backwards at certain pedal cadences. All my bikes have exhibited this tendency but I thought the Q-rings made it more pronounced. In any case once cadence gets sufficiently fast the rocking diminishes. One artifact of the rocking with the left roller 2" further to the left was when the bike rocked backwards the rear wheel would momentarily disengage from the rear front roller and I could feel it through the front wheel as wheel slip. With the front axle almost right over the left roller the rear wheel stays engaged with both rollers.
Here's the view from the cab. I never see the front wheel but so long as I keep the boom centered in the screen and my legs aren't hitting the orange snow pole on the left, and my right elbow isn't hitting the support on the right then I am on the rollers. I use a floor fan for cooling that can be turned on and off through a remote control.
My performance has improved from my initial 10 mile avg 7.9 mph to 12 miles with avg 10.0 mph. There's still plenty of room for improvement. I am riding in the little Q-ring chain ring. On the road that ring has a maximum speed of just short of 20 mph.