Nothing difficult with using single tank sidemount. If you have not problems with bouyancy - you will have not problems with single tank.
Just put some more lead on the opposite side of the tank, and have a pleasure.
some examples (when I had dives to the shallow, deeper 20m I try to use two tanks):
There is 10L steel tank, not big and with sinkancy around 2.5(full) or 1(empty) kg
Also I even try to use short and heavy 12L steel tanks. Not so comfortable, as slim 10L, but also swimable.
And I use it even with FFM
Some notices:
If you keep your octopus like on the stage bottle - always remind your`s buddy, where it is. or share your main regulator, and than use for yourself attached under the rubber rings.
It is nice to have lead weights not on the belt directly, but inside some pockets. I have four - two on the back on the belt, and two on the shoulders.
And have one small (approx.1 kg) lead weight.
You can easy adjust your trim just moving this small weight between pockets. underwater.