I thought we were talking about sealing not removing? After having installed I would guess hundreds of portlights
and repairing many that were leaking I stand by what I said. Do the research
and study the manufactures web sites you will come to the same conclusion. Lots of bad information out there but the facts speak for themselves. I recently wrote a long article about sealants I have just not had a chance to publish it yet if you would like a copy PM with your email
address and I will send a copy.
Also to the OP are you bedding a plastic or metal frame or the glazing (IE glass, Plexiglas ect?)