The model 18 is a rather small stove - 1.3 cu. ft. firebox. Even so, it should provide substantial heat. But if you really want a stove to be your sole heat source you probably do want something more in the 2 to 2 1/2 cu. ft. size range. Shoot, probably 3 cu. ft. would not be
If you are new to this then you do need to work through the questions you are going to get. My first comment is to the quality of the wood. Sycamore should be dry if it has been split and stacked two years, but the btu value is not that great. With such a small firebox you may simply be unable to load enough at a time to get the stove as hot as you would want.
Which leads to the next question: Do you have a stove top thermometer? If so, what kind of temperatures are you getting?
Finally, someone recently pointed out on these forums that there is little point in trying to purchase a more efficient way to heat the outdoors. Have you really looked into the various places you are losing heat - doors, windows, gaps in seams, sloppy dryer vents, etc., etc.? Cans of spray foam and tubes of caulk are really, really inexpensive. And is your insulation up to snuff? Is your doublewide on a foundation or is it up on blocks? Either way, are the floors insulated as well as they need to be?