Captain's right, level cruising isn't part of this 2-channel package.

Check out http://www.youtube.com/watch?v=aT-IH_jKhCI

I think I didn't engage bow thruster at all in this vid, and had no bow planes.

My Wally sub had a downward trim, and stern fins had some silicone tabs that contributed to downward drive.

Note my sub was trimmed to ride with decks awash when at rest. So I didn't care to follow the Wally manual, and had myself a sub riding about as high as an authentic LA-class sub. My planeage and downward angle managed to push all that underwater; if you set your waterline like in the manual, though, (and maybe remove the foam from the conning tower) you shouldn't need as much downward planeage and push as I used. If you use enough, your sub should stay under whenever you impel it forward.

When the sub went under, immersion of above-waterline structures generated enough buoyancy to pop it back up past the at-rest waterline and until it lost momentum; then foward drive and planeage pushed it back under.