Hmm, back in the good old days (4 line c kites were 99% of the kites on the water) the rule of thumb was if you cant walk it back up the beach then you are too overpowered unless you REALLY know what you are doing.
I would not suggest a 5th line on a c kite as a way to depower the kite other than as a safety and/or emergency and/or for relaunch purposes. The kite ends up being too unstable with the 5th line pulled tight.
However with your 4 line setup, have you tried pulling in the depower strap a little (or a lot) more when you are walking back up the beach?
Also, are you walking with the kite over your head (bad) or at an angle? depending on the direction the angle and the proximity of kite munching trees having your kite lower may actually help you walk upwind
Besides, more time doing the walk of shame gives you the opportunity to contemplate the important stuff like:
- why can't I get up wind?!?!?

