Long story short. Been using waist harness for years, but because I do heaps of jumping I think it's taking its toll on my back, I do prefer a waist harness, but hoping a good seat harness may have to be the go.my question is, will the v8 dynabar hold up to heaps of jumping? And will it cure the back using a seat harness?
Oh and will I look like an overgrown baby with nappy on?
Blaaaaaaaaaah!

Yes. Maybe.
Who cares?

Board shorts harness with the dynabar is the go!

Have been running the Dakine's with sliding spreader for quite a while now and absolutely love the setup

Nitrous shorts and a Dynabar! +1

Sounds good, but would that combo stand up to jumping a lot?do the shorts have the same support and comfort of a normal harness?must say, they look good but never tried them.

I don't think a seat harness is going to solve your back issues if the issue stems from jumping too much. I imagine the cause is compression of the spine from hard landings or is it from take off torque on the upper body where the waist harness is located? Your back will still feel a hard landing in a seat harness and using a dynabar your still going to get torque on the spine if the hook is out to the side.

I use a seat harness as I can't have the hook above my belly button if I wan't to kite for more than 10 minutes. The seat harness lowers the effort to a point where I can comfortably kite for hours. If I start jumping a lot it still gives me grief, so I've just decided to limit the amount of jumping I do. Having said all that I've used the dynabar and various seat harnesses for years without issue. The Dynabar is rock solid with a couple of serviceable parts that you'll swap out every year. Seat harnesses on the other hand seem to wear pretty quickly. I've tried:

1) Dakine board short harness; extremely uncomfortable (plastic reinforcement on the side not padded enough), excellent centre of pull for me, destructed after about 9 months of 4 days a week activity.
2) Dakine nappy; looks terrible if you care about that, excellent comfort, good centre of pull, destructed after about 12 months of 4 days a week activity.
3) B2 board shorts; very well made, good comfort, centre of pull with a dynabar is almost the same as a waist harness which is a negative for me. I have to really crank down on the leg straps to lower the centre which takes away from the comfort a bit. Noticed one of the buckles doesn't stay tight after only about 4 months of light use (damn this season!)

release back stringiness first (that are the reason to compression .... nerve pain )
then working on muscles (abs ang legs most) ...once or twice a week
streching few minutes before and after session (should be made when stringiness is released otherwise is worse)
out of water 10 minutes before extra tired ( not easy to do)
no extra weight (easy to say)
do not complain ......no excuse..... work on it ......hard anyway to be in good shape.
seat harness ...waist ......yumping....waves ..tricks...age..... dynabar ....da kine ...ride engine ( all secondary)