I have been dialing in the outfitting on my Piranha Speeder and having a strange effect. To start I am 5’11" and weigh 190lbs, the boat will rarely have anything in the bulkhead other than a gallon of drinking water.
I started with the seat in its “factory” setting, full forward adjustment. I noticed the front of the boat was deeper in the water than the stern by nearly an inch. (Determined by river scum marks on the hull after pulling the boat). The tracking was straight and neutral during glide at this point. I moved the seat back to give myself some knee room for wet entry, the wetted surface is very close to even from bow to stern; but now the rear wants to pull out while gliding. This is happening in still water, unaffected by wind or edging.
As an experiment I moved the seat back further making the stern lower in the water and this makes the effect more pronounced. While paddling, when the front is nailed down by the boat cutting the water the stern is very loose even though the skeg profile of the hull is under water.
The Speeder has very little rocker and no chines, it is very rounded in the center, the nose is chiseled, and the rear mirrors the chiseled front for a longer water line.
This entire situation seems opposite of every other boat I have been in. I am used to boats with pronounced rocker hulls, and can effectively change handling by moving weight around. This is not really a problem, I will adjust the seat back to make the boat more neutral; I am just a little confused by adjustments not doing what I intended them to do. What is my stupidity making me miss? Or is my entire theory wrong?
FWIW, found this long review
Found this review from the UK, where it seems they really ran the boat thru its paces. In case any of it resonates with you: http://www.canoekayak.co.uk/Articles/Pyranha-Speeder-flatwater-kayak-test/_ft74_tp23_cat12
Looking at your other boats, it's not like you aren't used to a variety of behaviors. But I only see one other moving water boat, and that is a crossover so likely more compromised in its designed features for WW than the Speeder. While the review I read said that in the right hands the Speeder could go out for some coastal paddling, it doesn't seem that the designers intended the boat to live in other than a river.
Maybe you are pushing the size and height on this boat. If you are, it will do more of what it is supposed to do for its WW personality, which is to squirrel around.