I'd like to know what people's suggestions are regarding whether I should use a seat or waist harness? I'm 39, ride a 5'10 surfboard with straps, usually a 9m kite and am into wave riding more than tricks. I use a waist harness because that's what I learnt with. I have a dodgy lower back with intermittent pain and some sciatica. I have seen a doc/had a scan and its mainly degenerative changes/getting old. Which harness would be best?