That is absolutely correct about the Landing Gear block.

I fibreglassed mine in but some well placed tri-stock is also a good option.

I had a look at mine last night and decided to give it a revamp. Still deciding on whether to keep it glow or go to Gas power (or even Electric could be fun but the replacement of batteries may require me to add a hatch, not a problem if I am taking the covering off anyway). I have a very lightweight prototype 23cc that I made a couple of years ago and it would work well (Might be too much power though - it turned 18/6 props easily)

On mine, I also
Pinned the firewall with some toothpicks, added a little reinforcing at the back of the canopy area above the wing saddle (Can't remember why I did that) and used larger wheels because we also flew off grass in those days.

Yes, any of the current beam mount 20's would be fine to use as they are narrow enough to fit well. The landing gear would be ok for a 17" prop but not much larger. I have a few alternatives here that I could put on mine to make it taller. It will probably become a Winter Project for me (It is summer here right now) and I will have it as a "throw it in the car and go" plane.