Do you know where your port timings are at? I'm not really sure where a dune port actually falls in degree wise but if the builder set it up for a dune port, I wouldnt touch your base gasket. I dont wanna give you wrong info, but almost every 4mill stock cly ive been involved with, we had to cut the domes. Best bet is to talk to your builder, tell him where your at with comp and squish, and inform him of your deto issues. See what he has to say. You might be able to send him your domes, and he can hog them out alil.