I tried a Libra Hackabout 4 years ago and hated it, so uncomfortable, it used to rub my thighs when doing a rising trot ( not soft leather ) and you need to be less than 10.5 stone for these.
I now have a Barefoot London and love it, like sitting in an armchair I don't do the girth up tight at all and it never shifts even after a 2 hour hack. Only downside for me is having to use quite a bit of padding around the withers as my pony is quite high and getting on a bit so lacks a bit of muscle.
It took about 4/5 hacks to get used to the width, you certainly know you've been riding!
I have a Freeform Classic for wide cob Blaze. We hack, school, showjump, X country, and do low level endurance in it. She is very comfortable and so am I No slippage when riding but it is hopeless to try to get on from the ground unless someone holds the opposite stirrup.
Jasmine, my TB, hates the Freeform. She prefers a straight cut dressage saddle and goes best in a Heather Moffatt SBS. I would like to get a FlexEE for her when finances permit