Quote Originally Posted by zihowie
Any suggestions?
I'm no expert (ok...to be honest, I am a professional woodworker)
Sounds like you are using the wrong tools for the job. A picture of your cabinet would help, but why not buy/borrow a hand saw? I'm pretty sure that beating the shit out of your future growcab is counter-productive. (and it is likely to cause more stress when/if you fuck it up)

Altho I would never do this myself, (but then again, I have the tools to do it right) you could drill a series of holes along the line you wish to cut, then use the sledge hammer or saw to complete the job. (kinda like connect the dots)

What are your plans for providing ventilation?