How large of a drop are you anticipating? I think that 11mm PMI weighs roughly 8 pounds per hundred, so you are simulating about 600' of rope weight. I think that most people who do that sort of drop do move up from a micro rack to a 14", at least. I see no reason why the rack in the link would not be completely adequate.
I am roughly the same size and weight as you. I've also been using a micro-rack for short pits and playing with added weight in the tree. I have been able to descend smoothly with 80 lbs. of rope weight (giant air compressor) below me. You didn't say what sort of frame you had. I started with the short (8") frame and found that I was too light to get a smooth ride out of that. The 10" made a huge difference and that's what I'm using now. If you have a BMS micro-rack, you can buy a longer frame from the manufacturer (Carol Basset, who will "tune" it for you), though I got one more cheaply from GGG, which considering your location would probably be the better choice.