Thanks for the beanbag/ricebag advice...did not think about, but similar concept to upward shooting .
I could use tripod when sitting, but not laying down.
I have a buddy that will lend me a gimbal head to test drive once I make a decision. Is a gimbal head overkill, good idea or a necessity?
Have to be careful about that ricebag... Don't use real rice if you're in tropical areas. I tried a DIY one, was fine till one day I found beetles all over my bag... was wondering where they came from, especially when they kept reappearing despite multiple "vaccuum treatments"... Finally realised it was from the bag =(
That said, I made a new one with a handful or two of uh... "borrowed" styrofoam beans from my sister's beanbag... Works a charm. Might want to get be wary of getting it damp though - I carry a waterproof foam mat around for that as well, just in case.
And if you're lying down a lot, you can always consider a yoga mat from Kmart or Target or whatever store is near you - they're cheap, light, easy to carry around in a pinch if you ever want to do some low angle shooting
Sorry, gone off tangent. Get the 300mm IS imo, even with a monopod the 400 isn't going to be easy to handle