Having done several DIY projects for myself I'm starting to get requests from friends. The most common request is for underquilts, specifically cooler weather UQs which leads me to a quandary, scratch made UQs are great but my skills are such that they require a fair bit of time and effort, conversely Costco mod UQs are quick and easy (especially when I make the friends rip their own seams) but aren't all that great in colder temps, even with extra fill.

I've been toying with different ways of making Costco quilts that are serviceable in colder temps. The faux baffle idea is intriguing but seems like almost as much work as making a UQ from scratch. Which leads me to the idea of a double layer Costco UQ. Does anyone have any thoughts, or better yet experience, with making a single UQ from two Costco quilts joined at the outside seams? I realize the extra two layers of shell will add a little weight but I'm wondering if there would be a substantial insulation gain from the airspace in between two quilts. To eliminate coldspots I was thinking of offsetting the layers such that the baffles from one layer overlapped the sewn through seam on the other layer, either by offsetting the baffles or by using a horizontal baffle on one layer and a vertical on the other.

My goal is here is to make a 30ish degree UQ without substantial investment of time or cost, but I'm willing to give a little is on weight.