There are a few things you should check/do to an ARF. One is to make sure vital areas are re-enforced since oft times the firewalls, landing gear mountings, etc. don't have a lot of strength there.
I don't have the 40, but I do have a 90. I re-enforced the landing gear mounting area, partially because I didn't like the way it was set up and partially because I used a taller, thicker TNT aluminum gear. I did knock the landing gear out of it one day when it hit a rut in the runway on a hot landing (new tx and I was having problems getting things trimmed), but basically it's been a great mod and can take a lot more than the stock gear which tends to bend on some hard landings.
I did quite a bit of research on the nylon vs. steel landing gear bolts. The opinions expressed above are the nylon argument, except no one mentioned that when the gear comes off, the wheel pants will punch holes in the wing covering. Some say take the wheel pants off to prevent this. The steel argument is that you don't want the gear to break off at the bolts and punch holes in the wing, but the down side is that you must repair the fuselage if you do knock it out when using steel bolts.
So pick your poison, but I would suggest beefing up the mounting area no matter which way you decide to go on the mounting bolts...
