Starting a turkey Flock

We have seventeen turkeys and we are planning on keeping the majority of them.  it is a mixed flock of slate and royal palm. We received them in the mail in July.  there are at least two toms of each variety, actually around 7 have been showing male traits.  We are planning on hatching our own eggs and then selling the offspring as meat.  We feed them gamebird feed and they free range the majority of their diet. the rains have been steady so our property has not desiccated into a fire hazard so i have not mowed all year.  the grasshoppers were once thick but the turkeys are clearing them out.  they are also eating a lot of mature grass seed.

The main concern is overwintering.  i have a rabbit herd and they have already taken to roosting in that barn, which is nice because there is an underground water line from our pressure tank in the basement  that runs to a spigot that works all year as long as i have heat tape on it.  We are in zone 4 Minnesota. there are some wild turkeys around but the winter seems to be a little harsh for a large native population to establish. we never really had them until the last decade. (thanks global warming). we also had possums for a quick bit but that polar vortex a few years ago snuffed em out around here.  Any advice on keeping these large birds happy in a building for long periods?

my other concern is how big of a flock is manageable. if we keep 8 hens an they each have 8 that's 64 turkeys and that is a large amount of land needed to raise them if its entirely free range.  Also how many Toms is too many?

i couldnt help but notice a lack of turkey posts on this forum and i am curious why.  is it that people start with chickens and are afraid of blackhead?  because i think that is overhyped.  hatcheries ship turkeys and chickens together.  blackhead is from a parasite not a virus and it comes from the soil, so in order to get it you need it present in your area to begin with. call your extension i guess.  otherwise i feel that turkeys are more permaculture than chix for meat, but the other way if you want eggs.  i will likely be proven wrong after i feed them over the winter.  

Personally I found turkeys to be more difficult to raise than chickens, the babies seemed like death magnets.  I prefer the personality and behavior of turkeys to that of chickens and hope to have turkeys again some year if I can get my act together enough to provide sufficient homegrown food for them.

Here are a couple links to information about setting up breeding flocks of poultry.  Looks like it calls for a minimum of three males:

http://www.pathfindersfarm.com/Spiral.html

http://www.themodernhomestead.us/article/Clan+Mating.html

Turkeys are roaming birds by nature, so it may not be a question of keeping them "happy" in a building over the winter but keeping them "happy enough."  Ours are in a mobile pasture shelter currently, and because I can't risk losing any more of them (a raccoon wiped out about half shortly after moving them out of the brooder), they are penned up all day, every day, and they decidedly do not like it.

If you have 8 hens, and they each hatch 8 poults, there's no rule that says you have to keep every last poult.  Sell the excess, until you're down to a manageable level.  The local predator population will likely chip in as well.

I imagine turkeys are less talked about in the permie context because they require more space, are more difficult to handle due to their large size, and are less easily marketed than chickens and/or chicken eggs.  And of course, anybody who reads the official line on turkeys will come away with the absolute certainty that they'll all die of blackhead in a matter of minutes...