I hate to add weight to the tail - it is just against all that I have been taught. [] After all a lighter plane flies better...

First I start by moving servos and batteries as far back as possible - this may not 'Solve' your problem, but it will reduce the amount of lead that you need.

Then; drill TWO holes in the lead weights and find a spot to mount them on the fuse (as far aft as possible) then drill two matching holes THROUGH the fuse and insert 4/40 'T' nuts.

Now using 4/40 bolts attach the weights to the fuse, the 'T' nuts will keep them in place - a drop of 'Locktite' can be used for added security.

Good Luck!