My wife and I have always shared a large 1-person quilt and 2 sleeping pads together. We've tried various ways to fashion the pads together. Straps or 2mm guylines work ok, but they allow air gaps which equates to cold spots. I tried glueing a strip of velcro at the edge of each of our NeoAirs, which would have eliminated gaps, but that glue was not strong enough to last more than a few trips. The best method we've found so far is to create a 40"x70" Tyvek sleeve to keep the two pads together. This is heavier and bulkier, but does what we want it to and has the added benefit of protecting our very expensive pads.
I'm aware of a few existing 2-person pads, with the Exped SynMat Hyperlite Duo seems to be the best rated. It is 28 oz, with an R value of 3.3 and costs a whopping $280. Klymit just came out with their Double V, but it's uninsulated and way too heavy for us. So, I'm back to trying to make a 2-person pad by combining two regular pads. I took my Massdrop x Klymit pads and created holes all along the seams on one side of each pad using a leather punch (borrowed, but these cost about $10). I strung 8' of 2mm guyline through the holes, basically sewing the pads together. This eliminated air gaps / potential cold spots. But, it put too much pressure on the end holes, with tugging on the guyline knots at head and foot. I'm afraid this will tear the fabric after extended use.
I think there are a few options to look at, with the best scenario would be some snug connector at each pair of holes. Some ideas:
Short lengths of guylines, with knots at each side, to pair each hole
Toggles, like MontBell uses (but I would look for something smaller), which would allow some gap but not a lot.
Something similar to a paper fastner, found in old-timey offices that still have paper products. Those are light and small and would line up the holes for no air gap. However, the brass ones have sharp edges, so I would need to find rubber or plastic.
Heat sealing the pads together with a hot iron. Not sure how easy this would be, but it would eliminate all air gap and simply the setup. Downside is that it would make the change permanent.
What other ways are there to couple these pads so they are snug against each other? How have you modified or thoughts about improving your pad?