Sooooooooooooo, whenever you are able to (as I did) try the HM saddle...............it's built in so doesn't go against the rules!! Every now and then I ride a horse (not my own) at different riding schools. SO, I get to experience first hand the difference and this leads me on to ask (out of wonderment really) about the experiences of those who've said the SBS "feels" hard.
When I had one I would have agreed that sitting on the saddle plus seat saver felt very very different. It did feel more firm I suppose but at the time I put that down purely to the difference, i.e. saddle beforehand, then saddle plus some extra "bulk" for want of a better word. Then I gave it a bit of time (can't remember how much time - might only have been 5 mins, could have been several rides). I wasn't satisfied!!!!!!!!!!!!!! I wanted a different saddle altogether - one that had it all "built in".
Someone said in a post above something about not feeling lopsided anymore (or something to that effect). My experience was the same, and then much more so when I could eventually afford the actual saddle - which of course is constructed by other means (in addition to the SBS material) to achieve this effect.
My experience (being the story of only one person) is anecdotal I know. BUT, I often have a bit of a laugh (and not from cynicism - it just makes me feel just a tad proud of myself - which is something I very rarely if ever do re my equine "prowess"). Because I KNOW that however loose the girth is I must be balanced (side to side) ..................... I also know (because of endless experiences to date) that if my instructor (I usually have the same one but sometimes do not) rides my horse during my lesson at my request) - he/she ALWAYS tightens the girth as soon as they get on. Their behaviour is automatic (as it should be btw). They are not tightening the girth because they think I should have done (they would have asked me to tighten it when I was riding). They are automatically checking the girth of the horse they are about to ride - and finding it slack!!
I've rambled on too much and probably confused everyone - so apologies. I'd never ever get an "A" for being articulate - but then I'm a Geordie by birth.