I'm thinking about getting a new tandem boat, primarily for playing in
easy whitewater (II-III). My wife and I currently (and will continue)
to paddle our old XL-13's solo, and we have an ancient Blue Hole 17A.
We want something smaller and more responsive, that would be more fun
to play in when we paddle tandem. For those in the mid-Atlantic, I've
paddled up to the lower Yough solo in my primea few years ago, not
recently, not sure will again. We're both comfortable solo boating
the Bloomingon run, have done Lehigh just below White Haven at
moderate dam release levels in our 17 footer. I'm seeking opinions on
two related questions:

1) Would we be better off with something rather tame, like the Legend
15 that Mad River is bringing back, or something like the Vertige X or
the Caption I hear Mad River is bringing back?

2) We both have bad knees, and kneeling all day is really hard on them
(many years ago my orthopaedist suggested I find a new sport). A lot
of our paddling is class II separated by moving water, where sitting
would provide relief. Our old XL-13's have the old Perception saddle,
and we like the seat option, but with it up around gunnel height, it's
too high even for the mildest of rapids or high wind. Assuming we end
up going with a purere whitewater boat, what are your thoughts on:
a) custom pedestal, with back wide enough to sit when desired,
but lower than the old Perception rotomolded seat? Is this feasible?
How hard would it be to do? It's O.K. if the sitting position puts
the weight a bit too far backwards, but need to ensure that when
kneeling the boat is balanced properly. Advantages: solid pedestal
outfitting for whitewater, not having to worry about getting feet
caught under a seat.
b) Even though it's a whitewater playboat, go with mounting
seats, not a pedestal, along with thigh straps. Advantages: obviously
works for sitting, still allows kneeling. Disadvantage: seat goes all
the way across, with feet underneath, probably higher kneel, less boat
control.