new guy needs a little help

[RG5400]

Hey guys, just bought a Mr. Heater 45000btu heater for the garage im tired of freezing my **** off in the winter months, I bought the heater and the 3" Mr Heater vent kit, my question is I have a flat roof (easy) then most, if i am running a 3" vent through the ceiling How big should the hole be in the roof??
I have no drywall in ceiling Now I want to get the vent pipe in before the drywall guys comes. Also Is everything in the vent kit i need or do i need any other type of fire shield or anything that is not in the kit. I have the heater mounted to the ceiling with a little drop down.

I have the kit Mr. Heater told me to get
http://www.ebay.com/itm/13064406513...NX:IT&_trksid=p3984.m1439.l2649#ht_2087wt_948


I just want to make sure I don't need anything else before the drywaller seals it up.

any info would greatly be appreciated.

 

[rustyjames]

The B-Vent thimble in the kit you bought will provide the 1" space required so you only need to cut the hole a little larger than the thimble sleeve.

 

[RG5400]

Thank you so much, I thought that was the case but I wanted to make sure I wasn't missing anything before that drywall goes up.
again thank you.