Its a Fact that Testors Metalizers don't stick to the plastic as well as paint.. thats why you should always use their Metalizer sealer over it.
I just built a Ford Trimotor, painted in overall Model Master Aluminum Metalizer, then sealed with Metalizer Sealer.. and after that dried a light coat of Future Floor polish.
Then I masked it off to paint the gloss black areas and didn't have any problems at all with the masking tape taking off the metalizer.
http://home.dejazzd.com/delbert3/Fordtrimotor/Fordpage1.html
also I used tamiya masking tape..my favorite
though I will admit i had a little tape bleed under in a couple of spots... lol