This is just my opinion, but given the choice, I would not cut them. I have read that it could force it into survival mode if you go to heavy. Tying may be an option, but for $5-$7 per, you can go to Home Depot and pick up 2-4 clamp lights with metal domes... the bigger the better.

Get some CFLs and just clamp them down low and direct them up to the under branches. You may even be able to clamp them right to the pot itself.

They look like this:
http://www.skycraftsurplus.com/index...ROD&ProdID=868

Easy cheap way to light the lower parts of your plants.