This blind structure is very tough for 12 minutes imo as it's only 25 blinds. We have a similar game with about 8 guys every Friday. We start 10/20, then 20/40 and then go 50/100. The rest is virtually your structure. It gives you time to settle in for 20 mins and our games finishes usually within 1 to 1.5 hours. Be ultra aggressive stealing blinds when you have anything decent in your hand Enjoy