Just practice some more. Ride toeside and chase the kiter in front of you but jam harder and overtake them on the upwind side (leaving them plenty of room and keeping your kite well away from theirs).
For surfboard riding, also practice swapping feet. Riding heelside is less tiring and you will always go harder upwind than riding toeside (unless you can twist your back about 270 degrees.

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Once you get good at it swapping feet is the best fun and can be done in an instant without thinking about it. When you combine it with strong toeside skills you will be having far more fun than anybody else.
In general you always want more weight on your front foot with your back foot trimming. You only load your back foot hard when you are *well* powered up and want to jam even further upwind.
Even on a strapped board don't get your feet welded into the straps. It is often better to have the back foot on the deck in front of the back strap. My front foot is often to the side of the strap with just my big toe touching the strap.
You might want to wax your deck between the pads and/or wear booties to increase grip. Also open your straps so they are easy to get in and out of.