Don't skimp on the push rods or the rudder servo. I think I have Hitec 645's on the Rudder & Ailerons and 465's on the elevator. Not the best but I had them available so I used them. Seems to work ok for me. Suggestion: use what you have. You can always upgrade. I have my Saito 100 mounted inverted and I also have a 14 oz tank. I just had to make the opening bigger to fit. Never had a problem drawing fuel. As for the landing gear here is my take. I have knocked it off maybe 3-4 times in 4 years. The main problem was the field I used to fly on. Many mole holes etc. I actually knocked it off on take off. Its been over a year since the last time. If you knock it off from the standard install you get no damage to the fuselage. You just epoxy it back in. On the other hand the more you beef it up the more damage you'll do when you knock it off. Trust me you will knock it off unless you install a spring wire gear of some sort. Plus beefing up adds weight.
When you cut your cowl add fiber glass inside around the narrow and weak areas.
I hope this is of some help.
K.O.