Interesting question... The safety of this depends largely on the width of your kayak.

In my mind, the swivel motion would make it more difficult to pedal? It might also create an unwanted rhymic side-to-side tipping motion of the kayak, especially with the higher center of gravity caused by raising the seat. Aside from potentially tipping over, I assume that the side-to-side rhythm will create more drag and make for a less efficient ride? Again, this is simply my assumption... I could be wrong on this.

For what it's worth, I have not seen a swivel seat in any kayak. I have seen just about every other creature comfort, but not a swivel seat. I assume this is because the swivel will be prone to tipping the kayak.

Just my two cents. Take it for what its worth :-)

4in raise is quite a bit that alone would make me a little nervous and adding a swivel seat would add to that. Would you be able to lock the seat in to keep it from swiveling while peddling? What brand/model are you modifying?

It’s a 12 foot Seastream. There is a Seastream Facebook site and 4 inch lifts seem to be pretty common on this boat.

Below is a common seat mod those guys are doing. I want to turn it up to 11

11 inch rise in seat on a 12' kayak? Let us know how that works out for you on a breezy day.

I've fished a longish pedal drive kayak with a swivel seat for the past year or so.

1. If you want a swivel seat, get the locking swivel base. The problem is you'll often find yourself facing straight forward but your seat will be rotated. Ergonomically this is terrible pedaling posture. Very inefficient being that you don't have a solid surface to brace against thats perpendicular to the direction of force being applied. Less power transferred and increased injuries and fatigue. Thats a lose lose there.

No idea what a swivel mount looks like for the seat above.

2. Four inch risers are not extreme. Most Sit On Top kayaks come with seats that are pretty low. I would advise most people to raise their seat up a bit in a pedal kayak. Much more comfortable when pedaling and fishing at the same time. As for how to raise your seat, the above seat looks just like a pvc job. If that's what you're gonna do I would definitely use schedule 40 pvc. Look in the sprinkler/landscaping section of the hardware store for the dark gray colored stuff. Couple risers/nipples should do the job. This could be done with metal pipe as well but its gonna add quite a bit of weight.

Nice work! Curious what is the reason for wanting to raise your seat up?

It gives me a better angle to pedal. It also helps me be able to turn around to get to the crate in the back. It gives me a better angle to cast off to the side, it also helps with the foot room on the floor. If I wasn’t fat, I might not have needed to do it, but I’m real glad I did this. So much more comfortable

Interesting question... The safety of this depends largely on the width of your kayak.

In my mind, the swivel motion would make it more difficult to pedal? It might also create an unwanted rhymic side-to-side tipping motion of the kayak, especially with the higher center of gravity caused by raising the seat. Aside from potentially tipping over, I assume that the side-to-side rhythm will create more drag and make for a less efficient ride? Again, this is simply my assumption... I could be wrong on this.

For what it's worth, I have not seen a swivel seat in any kayak. I have seen just about every other creature comfort, but not a swivel seat. I assume this is because the swivel will be prone to tipping the kayak.

Just my two cents. Take it for what its worth :-)