No problem Crunchy,

The diving angle can vary greatly depeding on the size of the servo arm, the length of the control rods, etc. I always get this weird nervous feeling when I dive deeper with diving planes, you never know if you're going too deep and whether if it'll be your sub's last dive... Artificial ponds with a clear bottom is your best bet, I primarily use pools for testing trials or when old man winter hits in. If the servos don't have self-centering features, then a spring-load is your best choice.

As for WTCs, PVC is usually pretty cheap. Resin or bondo end-caps with O-rings give easy access and make a good seal. However, I don't own a lathe so I'm currently experimenting with metal cans for a cheap WTC source. There are some that come with a resealable plastic cap. I believe that if you reinforce them and add an elastic band around the rim, you should get a pretty good seal!