RE: Help! Need to add weights. Where?
Does your engine have the black flywheel ring around the prop driver? That flywheel is Steel, and quite heavy...you can press the prop driver out of the flywheel ring with a couple of sockets and vise.
This will save you from having to ADD weight to the tail...
You will have a slightly lighter and a more responsive airplane...wait to do this until after you've flown the airplane some and are getting bored with it.