I have just spent a couple of weeks sleeping on my new Big Agnes AXL Air 300 gram mat in Scotland. It is indubitably the most comfortable mat I have ever slept on, but it does suffer from being a tad slippery. I will be taking some of my own advice below.
(The dogs as you can see will not agree to being left behind again!)
Before you begin on anything more complex remember the problem can just be caused by an over inflated pad. For best comfort and stability the pad should be inflated just enough to keep your bum from touching the ground. That way your body sinks into the mat, making it conform to your shape. That is the secret of a comfy night’s sleep anyway.
The second secret to a perfect mat is to have it just about the length (and width) of your body. Any part of the mat which sticks out from your body will just fill with air which is not doing anything at all. In fact it is making the mat less comfortable as you will have to inflate it more so that your bum doesn’t touch the ground. I recommend shortening your mat to exactly fit your needs. You will also save a couple of ounces doing so.
But ‘if the problem persists’ as they say, then try some of these solutions:
- Roll something like a t-shirt up and put it under your mat beneath your knees. This will stop your bum from sliding down the hill. Eg:https://www.youtube.com/watch?v=fqlup8pgM7U
- Or put it on the mat (just like a garment at the top to create friction): https://www.youtube.com/watch?v=kpZTf8_NS-k
- Add strategic dots or lines of seam sealer to the mat : https://www.backpacker.com/gear/how-can-i-stop-sliding-off-my-sleeping-pad
- Add a Gossamer gear Thin light pad – this will also increase the ‘R-rating- of your setup a bit.
- Add a piece of anti slip grid matting approx 9 x 12 (such as you can buy from caravan stores) just below your bum.
- Thermarest non slip fabric spray such as this https://www.amazon.com/Performix-075815100139-Super-Fabric-Spray/dp/B000UDCC8K Thermarest used to sell a proprietary product which apparently worked well and lasted for years. You may still be able to find some.
I would be a bit careful using such spray-ons. Check them out on some cheap fabric first. Ideally you will want one which just makes the material of your pad slightly tacky (without increasing weight) and without attracting dirt! You will also want one which does not harm the pad.
PS: I notice the new Massdrop Klymit mats have an anti skid surface already applied: http://www.theultralighthiker.com/massdrop-in-stock/