Looks really good. You need some more time behind the sticks though I can see (and spring centering).
Just my observations from running full size machines (not often but a few times), would think it translates over into scale RC, and your not the only one I've seen run an RC one like that. Watch this vid and notice how most of the digging does not occur at the full reach of the machine, it's hard work way out there. Also notice how most of the digging is carried out by the stick movement not the bucket. The bucket is used to adjust the tooth angle along the path you are pushing the bucket with the stick and boom. When you figure out the sweet spot to run it, it will take alot of the load off the machine and be easier to get full buckets nearly everytime.
http://www.youtube.com/watch?v=guM8N...eature=related
Nonetheless though, very nice work! Should be a very fun toy.