Hiya, i had that too and tried everything too. i'd say in my opinion if you improve your core muscles it will work itself out. a quick test though, i heard you should be able to hold your position without your hand if you get what i mean. next time you're on your trainer and in your normal position just take your hands off the bars and see if your core can carry the weight. if not you'll have to start doing them sit-sup;-) this worked for me - it could also be fit either??