You can take an X-acto and ruler to make a hatch on this model. With a layer of wood or popsicle stick glued to the inside edges making a lip for the lid to lay on, and you can screw it down or fasten it with a release mechanism like this.
http://ecsvr.com/abm/ShopDisplayproducts.asp?Search=Yes Tower has some cheap $50-60 kits you can build to gain experience with making modifications. But the easy way before you assemble the ARF, from the wing saddle you can use epoxy brushes to work in the finishing resin.
http://www3.towerhobbies.com/cgi-bin...?&I=LXE269&P=7