Phillip, Drafts are common with quilts and almost nonexistent with bags except at low temps (<32F.) Before purchasing my 20F Long/Wide quilt from EE, I spent about 20 years using my bag as a quilt mostly. When temps dipped, I zipped it up and was fine almost always. A couple nights I was cold all night even with all my cloths on, but the temp dipped down into the low twenty’s and I only was set up for 35F. I got a long to supply some head covering (I am getting fairly bald) and a wide to prevent all the drafts.
Anyway, a couple weeks ago I was out in the ADKs when the temps dropped to 24F.
I was fine, here’s why:
1) I use a 5 layer NightLite pad as a pack frame in a GG MiniPosa. I put this pad over my Xlite.
2) I use a larger knitted cap as a balaclava. I pull this over my head and face at <32F.
3) I use loose, knee high socks as sleeping socks. If I get warm, I can roll them down.
4) I changed out of my hiking cloths, rinsed them near the local stream, and hung them. But, I wore two pair of long-johns: light and medium.
5) I have a down jacket, but I didn’t need it till I got up at around 0100 to take a leak. Then I got a bit cold walking away from camp and put it on. There was a heavy frost by then, my thermometer said 27F.
6) I am a side sleeper, so, I rolled part way onto my stomach and pulled the quilt around my back, then rolled nearly onto my back and pulled the quilt around my front and finally rolled back on my side. The quilt was wide enough to cover me completely.
7) I pulled the extra length over my head with just an air-hole left for breathing.
I went back to sleep and slept till about 0430 (about false dawn) and got up and got a fire going while I prepared breakfast. My thermometer read 24F when I woke. So, I think a long/wide will cover your needs. I have a Revalation so I can open it up when it gets warmer, but I pay with extra weight for versatility all summer. Only spring and fall do I actually need the long/wide.
Anyway, I think you have the correct temperature rating, but you could use the long and wide version. As others have said, a CCF pad on top of the Xlite will add about 3-5F to your sleep system. But, at the additional weight, you could also go for a good bag rated at 20F (WM 20F Ultralight is 29oz vs 20F Revelation is 22.5 + 2oz head cap + 5oz pad.) Note that at lower temps bags do better and are more thermally efficient than quilts, sort’a like mittens vs gloves. (I have a bag, Marmot SS #0 for colder temps.) Quilts are great at >32F. But break even or start hurting weights at below that. Yeah, it can be done, just not as efficiently.
Personally, I would recommend selling the quilt you have and replacing it with the long/wide version paying a couple ounces for the extended versatility of occasional nights down to 20F. Or, if you plan on earlier and later trips out, get a bag to cover that temperature range for regular use, relying on an extra set of long-johns and jacket to cover an extra 10F in temperature range (ie down to 10F.) Reserve the quilt for 30F and above, ie summer only use.