Internal Alu Mast sealing.

[Robbie.g]

We're talking internal mast leaks, on a 15yo keel step mast, looks like a painted alu fosters section.
So having delt with all the usual suspects, wiring tube (top end and all other entries), the swisscheese of a mast cap, hosed around the deck gaiter etc. there is still water commin in, definately internally. Opted for the internal seal, just below the lowest exit, found signs of a previous go. .etc etc
The chase; below is what i currently do, and what i use. I'm looking to improve the process, and the reliability, so i'm interested in what you guys do, and /or any ideas.

My current procedure when the mast is in place, is to drill a hole just lower than where i want the finished seal to be, (usually at the lowest exit),hose out and leave to dry; then insert a balloon and blow it up, this fills most of the void (except around the wiring conduit edges). I then squirt/pour in Selleys Allclear, this usually, mounds in the center then slides down adhere to the mast wall and the small voids around the conduit; Success depends on the tempreture real warm (skins too early and stays as a mound), or too cool (stays as a mound too thick to run). when cured I then add an other layer and remove the balloon. Works 1st time 8/10 times, although some, dispite my best efforts take 2/3 goes.
The re-works are killing me.

Cheers in advance.