Hi Dave. You have already been flooded with "expert" servo advice, so I will spare you mine.
Actually, I am writing because I see you are in ChiChi, a place I have great memories about. I was there for a couple of tours when the "Globies", the Ci24 Globemaster !! was the plane that few down to the ice and the pole itself. I made the trip many times, and was always glad to get back to NZ, its warmer weather and its great hospitality. Shared many a "cuppa" with Kiwi friends, many orders of fish & chips on the banks of the River Avon. I even survived driving a rental "Mini" on the wrong side of the street.
Every trip from the US down included a dealer box of balsa from Sig Mfg, intended for retailers and being a variety of sizes. The local club kept strict control of the contents - a member had to show plans and a list of what he needed before he was allowed to buy the wood, and had to show a completed airplane before he could buy balsa for the next project.
I am also a ham radio operator, and had many friends in that club. My last farewell party with them was probably more dangerous than flying down to the Pole. Eloy Marez.