Be a bit careful and observant. On our 42I, when slipped with the keel bottom resting on a plank on the cradle, there is a lot of force on the sealed joint between the fin and the hull. I don't think there is any risk of structural damage, but when we allow this to happen the sealant right at the top-front of the keel tends to separate from the hull. I imagine it could eventually begin to seep or leak at that point.
I know this doesn't help with what you're trying to do but when slipping our boat I try to support the weight aft with a big rigging strop connected to the cradle. This keeps the aft end of the bulb from exerting a lever effect on the front of the fin attach point and it seems to help avoid the problem I describe.