Trike gear is easier to ground handle with. When the plane is slowing down (as it will be often on a bumpy surface) the weight transfers forward. So that puts more traction onto the wheel that is steering you with a trike. That's why cars are all built with the steering tires in the front. A taildragger will save you a little bit of weight and can make engineering the front end easier. Given the terrain you'll have to taxi on, you might consider using a servo saver for the front tire. A metal gear servo might not be a bad idea either.

On the test flight, it looks like you've moved the wing back some. The tail moment is so short on the plane that stability is going to suffer. If you guys will use the Cunningham specs for your overall plan, I think you'll be much happier with your results. If the tail moment has to be that short, have a look at the Sig Wonder to see what kind of horizontal stabilizer area is needed to keep the plane stable.