IMHO I think that mixing of these 2 particular styles is not the best idea due to the philosophical differences in terms of fighting.
WC focuses on a strong base and of keeping kicks below the waiste. TKD on the other hand focuses on a lot of side stepping an opponent and of course kicks above the waiste. Not saying you can make adjustments but if you do I think you would end up showing more WC than TKD in terms of skills being shown.
I take TKD and Shaolin Kung Fu. At first I thouht they would compliment each other well but after doing it for awhile now I can say that they do not. TKD and Kung Fu stances are totally different. Ways to perform certain kicks are different. Also what makes a difference are teachers and their different philosophies in terms of fighting and the applications of techniques.
I have stopped TKD and will look into taking WC b/c I feel that those 2 arts compliment each other alot more better than TKD and Kung Fu.
I would say you may do better sticking to TKD and maybe using some concepts from WC that may help you.
When you cross train it is really hard to keep things seperate. Somtimes I would do a TKD form and the first motion would be a kung fu form and I had to catch myself. Also when it came time to spar I would be in a perfect kung fu back stance instead up upright and bouncing as TKD does.
Main thing to think about, WC focuses on closing the gap while TKD focuses on keeping space between u and your opponent. When it comes toreal life situations and which art is better then you have to see which works for you better. Most would say in real life situations, WC is better than TKD. (excuse they use, "Who in a real fight kicks to the head??"
Best thing I say would be to cross train in Hapkido. That is pretty much nothing but hands and you are a TKD'er which is feet so that would work great.