New UDS build

Ok so I am about to embark on my first UDS build. I have acquired a Drum as well as a Weber kettle off a local classified. I am planning on installing 3 tracks/brackets on the inside so I can adjust the height of the racks. I will use the weber lid, and pipe nipples with uprights and ball valves. I however have a few questions, 1 if I put casters on the bottom is there any foreseable issue with bolting them in? (I don't weld and would like to keep costs down). Also I live in Nova Scotia and the temp drops to -20 here in winter, so I am wondering how many air intakes would I need and at what diameter to be able to smoke in winter? I was going to go with 3 at 3/4" will this suffice or should I go larger or just add a 4th? Also to fit the lid on the drum some adjustments need to be made, is it wiser to grind off the lip of the drum, or add a strip of metal to the inside? I'm worried about rigidity without the lip in place. Has anyone tried cutting the top few inches off the bottom of the weber kettle and affixing it to the drum? I know some of these questions are answered elsewhere but the airflow when the temp plummets is one I can't seem to find a solid answer to. thanks in advance.

Ok thanks for the replies, I am keen to use ball valves more so than slide vents due to the fact that it is also quite windy here, figuring if I put uprights on my intakes there will be less direct wind blowing into them. Also the parts are readily available to me, whereas slide vents I would have to fabricate or order online, and shipping would add to the build cost. If anyone in a similar climate would weigh in that would be helpful, as of now I am thinking 4 intakes all 1" or is that simply overkill?