I have dealt with two people who sell Royal plans on ebay. I have a 310 kit, but honestly the hassle factor of making copies of these big sheets and shipping them is more than what these guys are charging. I have quite a few Royal kits, some with frail yellow plans that clearly would not survive the building process. I have bought 4 sets of plans from these guys; Bearcat, Lightning, Oscar and Tony. I am satisfied enough with the quality of plans from either of these guys that I will almost certainly buy an extra set of plans for the rest of my Royal kits to be sure I have the ability to do repairs and scratch (okay, plan not scratch) build more in the future.
http://myworld.ebay.com/u.s.wing/
http://myworld.ebay.com/wflawson/
If you do not see what you want on ebay, email me and I will give you their email address.
*edit - By the way, the Royal Cessna kit is of the 310Q model. 72-7/8 inch wingspan and 52-1/2 inch fuselage.
- Jan