Bad idea. I would leave the extra fly, bring a shovel (Voile Mini, BD or similar) and dig a platform maybe a foot or so deep before putting up the tent. Try to stay out of the wind, but be careful about putting the tent under a tree that could drop heavy amounts of snow on it.

Here's the deal - what makes a winter tent (meaning snow winter) a winter tent are two things - strong poles in a configuration that will withstand high winds and a body or body/fly combination that will block wind. Extras include a big vestibule and perhaps an extra door. Winter tents can be freestanding or a tunnel style design.They can be a single wall or double wall (body and fly).

What they are not is any warmer than a comparable 3 season tent. Any tent that blocks the wind will be as warm as the next one, generally speaking.

Here are some reviews from Marmot's website-read the last one by the guy camping on Grouse Mountain, which I happen to know is just north of Vancouver. I went up there for the day while visiting Vancouver a few years ago.
http://marmot.com/products/limelight_2p?p=118

As you can see from the comment from Marmot (the Nice Marmot), they do not sell the Limelight as a winter tent. But, under less than heavy snow and wind conditions, it will be fine. Some people use far less shelter than yours in winter-tarps and bivies.