I don't have an issue with it sagging while climbing but then I use a belt, leg loops, and set my bridge really short. Its basically as tight as any other 1 panel saddles out there. There is more chance for sagging because unlike most 1 panel where the belt is independent of the bridge, 2 panels webbings are longer to help with pinches but this also make belt placement troublesome. Once I am settle in to hunt, I start loosening up the bridge and belt to a comfortable setting. The thing with a lot of two panels setup, people dont like using belts or leg loops, so they often take them off completely. Especially since most are not load bearing or climbing rated, their purpose is to hold the saddle against you. I personally would never suggest not having leg loops or belt. I simply replace them with climbing rated straps and buckles. I also did a simple sew buckles set between the bottom of the top section and top of the bottom section. They stay clips until I want to adjust them in tree. The ESS you can clips the bottom to the top's molle, same with the Latitude Method I think. The new Transformer has straps adjustment too. I just did a simple buckle setup because I dont have a lot of sewing experience and even if it break the panels just slide up and down.
But again, its almost impossible to fall OUT of a saddle unless you're actively TRYING to. I tried one sticking with the TL Ambush Pro and it was alot harder. Probably because it was so bulky. The easiest was probably my RCH that I used for the RCH/SitDrag DIY. The main thing is to have a short bridge, so you have room to move.