I know this is a question for Ziggy (not me

) but I couln´t find weldbond so I used sikabond 540 which is a kind of elmers but it is water and humidity proof. I Apply it with a brush on both surround(of passive) and cabinet and used a rolled-up cardboard strip to fitt over the surround. if you do one at a time you place the cabinet on its side (with the port facing up) drop in the new passive (all glued up) place the rolled up strip of cardboard ,tapped so it wont unroll (roll up enough to cover the outside of the passive) and finally place some weight on top (a few big books should do it)
JUst thought Id drop in the thing about the cardboard as I´ve seen some people are going to the length of routing a special disk to do the same thing