I had to add two oz of lead to my 4* 40. I put some sticky lead under the horizontal stab and it all came off after the first flight. How should I hold the weight on?

You can trim away a little of the covering and glue the lead to the wood with epoxy.
I've also had good success drilling a hole through the lead and running a sheetmetal screw into the wood. If the wood is balsa (and not plywood) the screws might pull out.

The last time I had to ballast the tail, I monokoted a quarter to the underside of the stab, will not come off and you have money for the coke machine at the end of the day You might also look for a heavier tail wheel.

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!

Hi!
Agree fully!!! Nere ever add lead to an airplane...ughh![8D].
Move servos or battery or engine or lighter wheels or ...whatever but never lead ...please!
Light airplanes allways fly better and last longer than heavy ones.

I STRONGLY agree with bbbair and jaka...you can put a servo extension on the battery pack to move it back as far as needed to balance the plane, or move the elevator and/or rudder servo's to the tail to make it balance. This also gets rid of the elevator and/or rudder pushrods which further lightens the plane...a win-win way to solve the problem.

Adding weight just cuts performance. Here's a photo of a 4*60 I had where I moved both the rudder and elevator servo to the rear for balance.