Ground, I just finished my 1.20US with a Saito 1.80. If you do a search you will see that a lot of people went totally crazy on "necessary" mods to this thing: hatches, reinforcement, replacements, etc. I have a dozen flights on my now with some pretty wild and high G stuff. It is flying great. I built mine totally stock except for the following: Sullivan & Robart control horns w/allen headed screws and Dave Brown Fiberglass pushrods. It is a trick mounting the engine without a hatch, but i did it. I wanted to build with a minimum of effort and time. I have assembled four or five H9 1/4 scale size planes. Generally they get all the bugs out of their later runs. Everything on my plane fit perfectly except for the vertical stabalizer. it's foot was about 1/8" to long.

After the above expericence with H9 planes and this US in particular, at some point in time I will probably do the following two upgrades: (1) reinforce the landing gear plate and mount with 1/4" nylon screws; (2) put a hatch in forward compartment to gain access to tank and firewall area.

Just as a matter of interest, built as above, my plane balanced perfectly at 11.8 pounds with the battery mounted directly behind the tank that was mounted as far forward as possible. the CG is at 5" from the leading edge and working out pretty good there for me currently.