You can get a gelcoat repair kit and seal up the crack, if you use clear gelcoat you will still see the crack's but you will have a sealed boat. Grady dealers can order you a gelcoat kit to match the hull gelcoat color, some stock it. Boatlife works well, but will not prevent the crack itself from getting worse, just seal the crack itself until it gets bigger, if it does. What it will do is make sure the fiberglass and core below are sealed and do not rot over time which you need to do one way or another, either through repairing the gelcoat or using boat life. 5200 would work too, but persoanlly it is overkill and not specifically made to fix gelcoat crack's. Boatlife isn't really specifically made for this either, but atleast would be easier to remove if ever needed and I find it much easier to work with in small applications or tight spots, especially if you need to be neat. Gelcoat repair is the best option but reguires some patience and time to do it right. This is the only thing that will stop the cracks if done right. Regardless, sealing it is a good idea if possible. Some crack's are just surface cracks in the gelcoat themselves and not through the fiberglass, they still need attention, but are less serious.
To prevent new spider crack's, make sure you drill new holes in reverse to get through the gel coat before drilling the correct direction, otherwise you will have cracked gel coat. Not sure if Grady did this improperly on older models or if they had an issue with their gelcoat itself, it is possible that they did, older gel coats were not as good as they are now a days.
