Originally Posted by MT4Runner
for the Marinetex filler.
I'd strongly consider drilling the ends--so if it does crack there it won't want to crack longer. P-tex the holes.
I'd skip both of those materials and use the boat itself as the source of your welding sticks. Shave a little material from the underside of the cockpit rim instead. As a bonus, this will be a color match.
The full process of creekboat demolition through cracking
begins not with the gouges but with the flexing and stretching that happens at the same time. The plastic only has so much allowance for flex, similar to a thin bar of steel, and when it is done it is done. Typically, a creekboat is good for 80-100 good Class V days before the plastic is worn out. The warning sign is the start of the oil canning, which is symptomatic of stretched plastic. The plastic would like to sprawl out past the bottom of the boat, but the sides prevent that, and therefore the pressure is forced to go vertical. Once at this stage, full cracks will form from seemingly minor hits (I had one go in the pool!). You can repair that crack, but another will inevitably form elsewhere, sometimes within another 10 laps. This cycle can continue as long as your patience to weld.
There are more dramatic ways to kill a boat faster, of course, such as sending it empty and full of water over a waterfall. This often results in a full shredding.
There may also be ways to extend the life, as research in the Northwest is showing, by foaming out the area below your seat. The theory is that you will prevent the boat from flexing through that half inch of movement every time you take a rock. It doesn't just help directly under the seat, it also limits the motion of the sides.