Making a stationary trainer
 

Hi,
Before I start construction, does anyone see something I don't. I am looking at making something like this or maybe something like this or this or this with resistance magnets

If I go with the later style with 3 rollers then I plan to use 2x3 for the side bar and inset the floor rollerblade wheels into the bottom of the board, so it is lower. Maybe the base will be 1/2 above the ground.

Are these designs good, bad or indifferent? Are there other better designs?

The only issue is that my wife and I will be using it and my wheelbase is about 4 " longer. That is the appeal of the first design. If I go with the latter designs, then I have to have a way to make it longer for her use.

I also plan to have some sort of platform for dismounting.

For the rollers I plan to use a 2" inside diameter pipe with wooden inserts (turned on the lathe) on the ends with an upturn to keep the wheels captured.