hey bara
where are you riding? river?
a heavier, narrower board will typically go better through chop (google surfing tow board). many kite specific directionals for strapped riding will suit you better for this if you just want to blast around and punt occasionally
many "proper" kite boards are going lighter, wider and lower rocker for surfing mushy waves now too though, so you still have to be more specific to the style of riding you want to do when going kite board specific and spending the $$$
i'll assume you haven't put straps on the old banger and are just learning the ropes. try shifting both feet around to forward and off center of the usual spots you are using, try sliding them all over during a long tack, and see if you can find the "sweet" spot for those conditions on the day. my advice is to forget what your stance would be on a wave, and move both feet further forward so that board is more on the plane in general tacks (which is what you are intuitively heading towards by observing more front foot pressure needed).
keep using both legs slightly bent as shock absorbers for the chop, but that doesn't mean you can't lean back in your harness still and avoid the dreaded "poo stance". leaning back will also allow you to apply some lateral pressure with your backfoot towards the fins (my back foot is usually just forward of fins on board if trying to get upwind more - then shift back onto pad if turning onto a wave).
and keep enjoying - the options are pretty limitless.