Hi Joe,
It looks like you’ll need
- 1 m of 1000D
- 2 m of 210D for the tubes
- 3 m 210D for the inflatable floor insert (you could use less, but then you’d have to patch together multiple pieces for the top and bottom, which would be difficult to make airtight)
- At least four drain valves (front and back, left and right, placed near the seat locations – more valves if you want it to drain faster). You could wait to purchase valves after you’ve had a chance to paddle the packraft and determined what number of drain holes works for you. That’s correct about my reason for recommending the valves for the floor drains (they can be closed on calm water). I’ve seen this done in one other inflatable raft, but not in any manufactured packrafts yet.
I’m not sure what you mean by elongating and widening a seat kit to make the inflatable floor – the seat kit is just pre-cut fabric and a small valve, so you wouldn’t be able to use the fabric and the valve is too small for inflating a 100 x 18 x 7 inch volume (you’ll want a Boston valve for that).
For securing the inflatable floor to the packraft, check out the Tie Downs & Attachment Points page under the How-To menu. In the insert itself, you can seal tabs of 1000D between at the perimeter where the top and bottom pieces are sealed together to make strong areas that you can punch holes through. Alternatively, you could simply put straps over the insert from one side of the floor to the other. I would probably try to secure the insert along its entire length because any areas that aren’t secured will tend to bend and float up if the packraft fills with water, which would let much more water accumulate in the boat and slow the draining process.
Cheers!