Skip the front wheel block. Just adjust the trainer height setting to the next smaller wheel size, or lower if that is your preference. Just make sure your pedals and cranks clear if you go more than one size smaller.
With respect to hand pressure, using a higher front end is something I use all the time and recommend that others at least try. Here is the info I stole from my rocker plate post.
- Lack of wind resistance on the body riding inside. That is a difference that I find because you end up with slightly more weight on the hands and arms, because you don’t have the wind pushing your upper body back.
- To compensate for that, I recommend that people raise the front axle about 1"-2" [25mm-50mm] higher than the rear axle. This shifts the weight slightly back onto the saddle and off the hands and arms.