I recently acquired an old Bell Black Gold Wildfire hull that has a lot of spidering in the clear gel coat, especially at the stems, which is to the extent that I am concerned the gel will start to chip off over time.
In a thread somewhere in the archives here, Charlie Wilson mentioned the type of clear polyester gel coat that was used on Bell Black Gold boats, and is apparently now used on Placid boats. You could contact him and ask about it if you are interested.
I found a lot of low viscosity resins that are marketed primarily for the owners of gel coated FRP motorboats, or sail boats, or surf boards. I have decided to try System Three Clear Coat epoxy. This is a two part epoxy that is very low viscosity. I have tried applying it to some wood thus far (which has worked very well) but it is now too cold to apply to the boat. System Three advocates using this product for initial repair of gel coat blistering.
The System Three Clear Coat is almost watery thin when mixed and I think it will penetrate spider cracks as well as anything will. But it won't cure at all at temps below 50 degrees F, requires 3 days or more to fully cure, does not incorporate a UV blocker, and might blush when exposed to water even after it is fully cured. I am anticipating applying 2 or 3 light coats to the hull, then wet sanding and covering with a varnish or clear poly for UV protection.
I am also going to try it on wood trim, again covered with varnish, on the deck plates, thwarts, seat frame and possibly the gunwales. But I can't give you a report as yet on how well it works on the boat.