In addition to wave riding, toeside riding on a foil was one of the main reasons for me to get another foil after so many years. I missed it.
Going well upwind I think it is just one of those things that needs a little fine tuning. I am just assuming what happens is that you follow the kite too much instead of leaning in properly and taking advantage of extra power from the apparent wind. Now the problem with leaning in is of course if there is a drop in power from the wind you are likely to fall forward so you need to be infront of the board as it were (this is me trying to find a way to express that you have to predict a bit what will happen). You have to be able to feel small differences in power and adjust.