So for the second prototype I have dropped the diameter of wheel #2 to 90mm saving 10mm of boot height. With this choice the prototype has a front mount height of 95mm and a rear mount height of 101mm. So the rear is only 1mm higher than more conventional skates and it still has 6mm of pitch. Of course a third prototype could shave these a couple more millimeters. One could use 84mm wheels for position #2 but I did not find that choice acceptable. Because of the angle at which I photographed the frame it gives the illusion that the frame top will be level or parallel to the ground. This is not the case. The rear end of the frame has been "jacked-up" off the ground an amount which provides the 6mm pitch. This was done by moving the axle holes lower than normal toward the rear of the frame.
The result is a frame that is perfectly stable with a standard 6.5 inch mount spacing speed boot. So I did not have to wait for the new 7.5-8.0 inch mount boots nor have to spend any money for a new boot. The price one pays is that 90mm wheels are almost nonexistent. At the moment I am only aware of one 90mm rollerski wheel which is made in France. I did not care to wait for shipment from France so I ground down a couple of 100mm scooter wheels to 90mm.
The situation is not much better for 125mm wheels as Yak Research distributes only two -- red 78A hardness and blue 85A wheels. But they are is stock in the US and available quickly and cheaply.
I was motivated to go to the 125mm wheel because I had worked out a theoretical model for power loss or "rolling resistance" some 6 years ago and knew that they would have a significant roll advantage. What I did not know when I embarked on this project was that there would be additional advantages to the 125mm wheel which have still not ceased to amaze me.
Now with the smaller wheel skates I have used there has always been a limit beyond which I learned not to go. Either a feeling of instability or lack of control arose or the skate reached the point of diminishing returns where pushing harder was barely rewarded with increased speed.
With the 100-90-100-125mm skate the rules are rewritten. It is ok to push as hard as you can under almost all conditions. There is never a moment of instability and in fact I have never felt more in control. And along with this increased control there is increased speed. Every bit of push or contorted body momentum you throw at it, it reponds positively and screams for more. No matter how hard I try to push it to reach the skate's level of incompetence it only reveals my own by leaving me literally breathless.
So I find that the 100-90-100-125mm skate has improved roll, improved control, and improved powering. The reason for the improved roll with larger diameter is pretty clear. But the control and powering issues are not so clear and never occurred to me until I started testing. I believe that the control and powering issues are linked to one another and rely on the "Hi-Lo" nature of the frame. That is, the front wheel is 100mm diameter and the rear wheel is 125mm. Consequenty the front wheel spins some 25% faster than the rear wheel and has a corresponding lower circumference. The result is that the front and rear wheels want to naturally turn at different rates. This appears to result in a stroke which is different from the small wheel skates. It seems that the improved control indicates a "self-correcting" stroke where the skate corrects for significant errors in skater force application. And it applies the skaters force in a manner which produces more efficient propulsion.
Now the only drawback I see to this skate at present is the wheel situation. 90mm wheels are hard to get and lightweight 125mm wheels are presently not available at all. Because of the weight penalty it is likely that few skaters will want to race on it today. But this will change just as lightweight 100mm wheels have just begun to become available. And from another perspective, I believe that the 100-90-100-125mm is the best training skate known today. It is already training me on how the stroke should be done and by improving my control it gives me a much more powerful workout than the smaller wheel skates. You could consider it a form of "cross-training" from ordinary skates.