NorthernKitesAUS said.. !!?? What's downwind riding got to do with riding toe-side.
Disclaimer: Yet to do a proper long-distance downwinder
A proper down winder.....awesome...
They toe-side too
www.kiteworldmag.com/video/the-magic-river/I suppose on topic comment should be made... some thoughts...nothing new but might be a slightly different way of looking at the issue which lights your bulb!!!!
1). Do heel side runs work out an angle you can easily hold choose targets in the distance. - Use this as a guide for your toe side path..
2). Look at the edge angle you are holding when heel side and try to work out where board axis is ( front to back). it is not necessarily symmetrical. When you are going toe-side what sort of edge are you holding - similar to Heel side.. to get the angle you may be leaning over more than you think you are (=that axis is biased towards the heel side). So it is easier to over balance when less power from the kite and or slowing down. The solution as per Gateman - bend from the knee - this allows you to get the edge but keep your weight more centered over the board.
3). Remember when you first started getting the hang of heel side... That balancing act between going up wind (ish!!) and down-wind and the power in the kite..?? Well it is essentially a replay... what worked for you then replay.. The trick for me was to always keep moving .. so S tracking and flipping back to heel side re-loading and having another crack. If you don't already, when you are about to change direction on heel side, try flipping the board to Toe-side and then down looping the kite and follow it around to end up back on heel side going back.
My toe-side is never as efficient as heel side - = there is a power limit available and below that I do not try and track for any long runs on toe-side.. I mostly ride directional strapped in, on waves, until I loose the straps it is unlikely to improve..

Keep asking and give us an update...
cheers
AP