Budegan, I always drill & tap them while on the fork tubes.. First I drain the forks,, then insert a plastic barbed fitting in the lower drain plug hole,, then put about 10psi of regulated air pressure on that lower plastic fitting. That way when the drill bit breaks through it blows the chips back out the top & none enter the fork tubes.. Same with tapping, as the tap is screwed in the light positive air pressure blows the chips up & out along the top of the tap.Is this the thread you read?
If so, read the reply by the wingnut. All the inner fork parts are the same (seals included) so the forks will take the pressure (I think it's 6 or 10psi max). You might be able to drill and tap in place, but some of the drill filings will end up in the fork oil and do damage.