hi m4' and welcome. ell Im an oner of S rex x ( and T rex as well) . The two companies are totally seperate. But I have prchased of both companies and indeed have shared a drink ( or erm about 7 in one case

) with the pople behind both companies and the are both fine. Diff between the bindings? Just 1 is mat black one shiny silver --so basically just cosmetic.
Ive obviously used both type of knee bar. I am finding a bit of a problem with the wideness of the S rex and will be looking into getting some extra padding ( insulating piping has been mentioned above). Ive also found that when wearing shorts ( ie most of the times) the buckle on the knee strap digs in rather painfully so. The easiest and cheapest ( tho maybe not most stlish) way to counter this is just to cut the end of a sox and haul it up till it covers the tender bit of flesh.
On the subject of straps. You may have noticed ( on the 7's site) or in photos people using extra straps around the knee. This really helps and makes you feel more secure and 'as one' with your stilts. There are a couple of makes about, or improvise with some car roof rack webbing straps.
And yep where are you --there are probably peeps near you. And check out Captial Bocking next month --its the place to be what ever one's ability.