sea nymph gas tank removal / proximity to hull rivits

[Boomer]

Ok here is a question that the dealers cant seem to get me an answer on. I have several leaking rivits on my 1995 sc175 sea nymph the rivits are in the gas tank portion of the hull I am not sure if the tank rests directly on the rivits or not . I want to weld the rivits but do not want to melt the plastic tank or worse burn the boat down, does any one know if there is a gap? The reason I am hestitand on removing the tank is it appears to be too wide for the access panell in the floor. any ideas ?