Great! Thanks for the help guys. You think I should soak it in a brine over night to keep it more moist?
Wet Brine vs Dry rub does not equal a more moist meat..
in fact sometimes wet brine can work against you depending on the salt content. Salt / Sugar is a drying agent good for curing meat. i.e. long slow low temp smoking. A good dry rub will dry the outside a bit allowing the smoke to penetrate and build a good smoke ring.
You are trying to cook and hold moisture not cure this roast (I assume)
Temp and humidity is what is going to hold your moisture. Getting a good solid smoke ring on the outside of the meat will help hold moisture in.
200 deg is a safe temp for wild game with no curing agents (nitrates). You can go lower but there are risks. A pan of water will help you in holding moisture.
Typically in WA (wet side) we have a relatively good humidity level already that combined with the fact that you stated you are using a propane smoker also adds to the humidity factor.
When Smoking as the temp rises humidity will go down. Hence the earlier comment about holding as close to 200 as possible. My guess (Without knowing the weight of the roast etc) would be 6 to 8 hours at that temp will get you to your internal temp of 160 deg.
Personally for me I would stick to a dry rub for this type of game and do a wet mop at the end. Mop it a couple of hours prior to being done.
This is a really great article that describes the "Stall"
http://www.amazingribs.com/tips_and_technique/the_stall.html
