I have a 7 year-old daughter that enjoys the concept of "ramming speed" in her SOF. So far, neither she nor her various buddies have made a dent (in her boat, that is). With modern materials, the durability is probably not an issue as it may have been in the past. If it is a concern, use something like 16 oz. nylon instead of 12 oz. 9-12 coats of polyurethane and you'd have a reasonably hard time putting an errant hole in it.

Regards,

Marcel