Zipper Door I recommend a back door w/zipper or window for cross ventilation for hot weather. Being in a canvas tent without a back door or window is miserable during hot weather.
SIZE OF TENT: If you can't decide between 2 sizes of tents , go far the larger tent. I have never heard anyone say they wished they had bought a smaller tent. When people complain about the size of the tent, the complaint is the canvas tent is too small for their requirements.
FLY: Fly is always recommended. Sometimes during rainy days, canvas tents will leak where the canvas touches the frame. If this wicking/leaking occurs the only solution is to purchase a tent fly. The fly prevents any rain or snow from touching the canvas so no wicking/leaking can occur. Other benefits of a fly (1) prevents sparks from the stovepipe burning holes in your canvas tent roof (2) protects canvas from ultraviolet rays which deteriorates the canvas (3) keeps your tent roof clean from tree pitch (4) creates air space between the roof and fly which acts an insulation area which helps keep your tent warmer.
FLY SET UP: The fly rests on top of the tent ridge and fly extends 8 - 12 inches on the sides. Usually, the tent fly has a 3-4" gap between the fly and tent eaves. This gap is accomplished by having the fly stakes farther away from the tent side walls. The gap is necessary to allow airflow to remove any moisture on the tent roof. If you are in Windy Conditions, you must not have a air gap because the wind will get under the fly and destroy the fly grommets and fly.
Tent Bag: I strongly recommend a canvas tent bag to keep your tent clean during hauling and storage.
Options: If you are not sure about a option I would probably add it. It is much cheaper to add options while the canvas tent is under construction compared to costs after you take delivery. (Been there done that!)
Color of tent: I encourage you to purchase a tent that is white. White reflects lantern light much better than off white or colored tents.
Purchasing a large tent: Large canvas tents, 16' x 20' to 16' x 24' can weigh from 90 - 120 pounds and can be very difficult to set-up. It normally takes 2 people to set up larger tents.
Cookshack. A cookshack costs almost as much as a tent of equal size. Sometimes it makes more sense to buy another smaller canvas tent to use as a cookshack and have the flexibility of using the smaller tent when less people go hunting or camping.
Color of Fly. A clear translucent fly is best as it allows light to pass through it. If you use a dark fly during the day it will be much darker inside your tent.
Reinforced eaves. The eaves have the most pressure on canvas tents due to tightening the roof by use of guy ropes and stakes. If a tent fails due to snow loads, the tent normally tears near the eaves and grommets. Insure whatever tent you buy has reinforced eaves.