"back in the day" we closed off the holes in the Betor caps.. for that very reason .. you got oil all over you.. didn't seem to affect the action with the bleed filled in..
It was also often recommended, to braze a cap over the top of the damper tube & drill sideways holes, to keep the oil from blowing/blasting up to the cap vents. Later Bultaco forks had a bent steel piece that fitted inside the spring at the damper end to achieve the same effect.
As Sleepy has pointed out, when emulators are fitted, the top of the damper tube/rod needs to be covered with oil at "top-out" rather than at full compression, as normal. Lots more oil in the fork, with potential for pneumatic pressure problems.
Anybody got a good Betor emulator story?
Cheers, DJ