To respond to Howard on the A700 a lot of spur choice is available. Take note that I am only running 64P gears so your mileage may vary...For 17.5 and USGT I play with a spur size of 78T to 84T but generally run 82T.
It also depends if you are running a spur dampener and/or witch version you run.
With no spur dampener you have a lot of choice but ultra slim spur or offset spur may be a problem with the placement of the locating pins.
I prefer machined spur with a flat surface all around with about 3mm of thickness on the the SD1 (also need to drill two 5mm holes)...PRS is the way to go if you are able to grab some. The SD1 is a good compromise but you are very limited on spur choice...maybe somebody can chime in on that. The ARC spur is flat but too thin and you need to be creative to make it work.
On the SD2 you can run almost any brand of spur gears but overtime the SD2 create some loose/wobble so I prefer a spur gear that have some thickness on the gear area like Robinson or Xenon VSS to limit the chance of stripping the gear.
If you run a higher wind motor class like USGT no real need to add the mass of a dampener
Whatever you run if you are able to find PRS spur gears grab some on carpet I am able to run the same PRS gear for a season!
My small list by preference...
- PRS...no SD OK SD1 OK SD2 OK (durable and perfectly straight)
- Xenon VSS...no SD OK SD1 not OK SD2 OK (durable and straight white so you see when the gear have debris inside)
- Robinson...no SD OK SD1 not OK SD2 OK (medium durable but cheap easy to find and straight)
- Axon...no SD OK SD1 not OK SD2 OK (on hand but never tried it seems durable and straight but on the soft side like the Robinson)
- ARC...no SD OK SD1 maybe OK SD2 OK (medium durable and not straight)
Short awnser go grab a PRS if you can get them or buy a Robinson lol