The main issue with seaing a Fibre Glass Dome is the flexure of of the material consequently should you nudge against the wall the base will move breaking the seal.
I used 1 mitre stud lengths cut them intop 6″ lengths using a heavy duty drill inserted around the dome. It is necessary to use a concreate to stainless steal bonding this is inseted into the predrilled hole with the stud length rammed down with a hamer ande finally cap this with a stailess streal nut and washer. I have around 20 of these in total. The door needs particular attention.
Lifting the dome wll as you go around the circumferance of the dome lifing section by section get all the sealent under the rim and bolt down.
Finally there is a product called “sticks like shit” that works well when mending brken clay pots amongst other things.
Best of luck