two layers of 4oz s-glass is plenty strong unless you plan on sitting on rocks and asphalt driveways as a general practice or weigh over 200lbs. I've got a 8yr old Pygmy 13 with a doubled layer of 6oz s-glass (don't ask) on the bottom and it hasn't worn through the first layer or dinged the wood at all,,and that's with tying straight on racks without bar pads. I've built two kayaks with one layer of 4oz and it's dinged the wood but held up fine. One kayak with a doubled layer of 4oz that's been through a LOT of abuse/use like sitting in the kayak on a ashphalt road or resting on rocks with a full load, 80lbs, and it's shown some areas of compression in the wood but it's very localized with any damage showing through on the interior where there was only one layer of 4oz, where there was compression on the outide layer and wood but two layers of 4oz on the inside there were no white fracture lines on the inside. I'm pretty sure that similar impacts on 6oz e-glass would have shown damage in the wood over a larger area. I did about three dozen test panels with s and e glass in a backyard test and the stuff is different,,tougher, slightly elastic, damage is much more localized without fractures traveling along the weave compared to a conventional layup of 6oz e-glass.

If you want ridiculous amounts of durability then one layer of 6oz over the hull with a doubled football layer works fine. On a friends Merganser I've got two layers of 4oz s-glass with a strip on the keel and there is no compression in the wood anywhere. I'm putting another layer of 4oz over the Coho I made with another football patch on the bottom,,,,ok so the boat will weigh closer to 48lbs when all the rigging and hardware go back on but I wanted to be unconcerned with landing a fully loaded boat on rock shelves. So it's got 8oz on the hull and 16oz under the seat/football area.

My vote is for two layers of 4oz with another piece for the football. It'll be tough enough.