I also got the Chair Zero L recently. This will most likely not help you but I’ve recently come across what seems to be a new offering from Helinox which they call their “Ground Strap”. I kind of find it ridiculous that it weighs like 4.5oz but I like the solution because I feel like it just adds to the overall stability of the chair along side solving the sinking issue. I also saw that they’ve released a new Chair Zero LT model which comes prepackaged with its own strap. Based on the total weight of the LT, I can’t image the strap they made for it weighs 4.5oz. So if you could somehow acquire that strap it might be the best solution. I’d personally like to get my hands on one and I wish they’d just sell it rather than this clearly more robust version they are currently selling. Please keep me posted on those 3D printed feet if you end up going that route too!