The reindeer hide and roll mat should be just fine. I have a number of friends who swear by the reindeer skins and it makes sense that they would conform to the shape of a hammock better than a rectangular mat.
For my own Hennessey I have used several arrangements, their own under quilt, a 3/4 length Thermarest (only part inflated), a large Ridgerest that has been trimmed to my height and a coffin shape, and various pieces of foam and mylar. The Undercover and Ridgerest both worked well. The 3/4 length mat left my feet cold. Cold feet are a common problem because you tend to sleep with your feet slightly higher, so circulation won't be so good, with undercovers, it is also very easy for an airspace to exist at the foot end. The 3/4 length mat was improved by using a few feet of cheap roll mat foam as an extender.
On clothes. Don't wear socks and keep the what you wear on your lower body to a minimum, no more than a thin base layer, if your sleeping bag is rated for winter. It is the same thing you find with gloves vs. mittens. If your feet and legs can share heat with one another you will stay warmer than if you insulate them from each other. The upper body is a little more tricky. I invariably wear a light fleece or light wool jumper and T-shirt except for high summer. I just find it easier to manage my temperature like that. I also use a thin wool or fleece hat and wool scarf. The hat could be done away with if you cinch the top of your bag over your head, but the scarf is hard to beat. I wrap it across my face and nose and breath through it. The outer surface can become soaked with condensation but because it is wool, my nose stays warm, and I get to breath pre-warmed, moist, air. I do not inadvertantly stick my nose in my bag to keep it warm, so making my bag wet.
You can shove any outer garments which you will want in the morning into a stuff sack and have them in the hammock with you, they keep warmer and are easy to find. Boots can have thier laces crossed and tied to the ridgeline and be left to dangle outside at the far end of the velcro opening. This keeps them easy to find, and out of the coldest, dampest air lying near the ground.
If you decide to go for it, best of luck!
