cold weather guidance

If you put your quilt inside sleeping bag it seems like there wouldn't be enough room so quilt would be compressed and not provide as much warmth.

Maybe quilt on top would be better

I keep reading that the best way to combine the two is to drape the quilt over the sleeping bag. This is especially true if it's a synthetic quilt. Your body moisture will end up in the quilt, and if it's synthetic it won't lose its loft as much as down will. I didn't bookmark anything and the only source I remember is on the Mountain Laurel Designs website (description of their synthetic quilts). I have seen this several other places, though. Also, as Jerry said, with the quilt on top you won't be compressing the insulation of either.

Depending on how cold it gets and whether you're a warm or cold sleeper, you will probably have to supplement the sleeping bag and quilt with warm clothing and/or perhaps a vapor barrier. Remember, too, that you'll definitely need a warmer sleeping pad or pad combination, with R value of at least 5.

You might want to try this out close to home or your car first, so you can bail out instead of shivering all night if it doesn't work.

I keep reading that the best way to combine the two is to drape the quilt over the sleeping bag. This is especially true if it's a synthetic quilt. Your body moisture will end up in the quilt

Maybe, maybe not. Where the moisture condenses is determined by several factors including the outside temperature, the relative insulation value of the bag and the quilt and the dewpoint of the air between you and the inner layer.

For short term use (a night or two) I'm not sure it matters where it condenses. I'm pretty sure that most folks experienced with long term winter sleeping will say to use a vapor barrier to keep moisture out of the insulation.

I've doubled up sleeping bags and/or a sleeping bag-quilt combination by putting one inside the other with good results. As mentioned it takes a roomy enough outer bag to pull off. If there's room, I think that's warmer than draping. If there isn't room, draping a quilt over the top should still make a big difference, one you'll have to test to evaluate.

I have done the same thing the past couple of year. Placing a smaller cuben quilt inside a larger quilt. Works quite well and the cuben quilt acts as a VBL.