there are a few ways we can go about this. one is to simply use a pad x/y calculator. either pad x rear or pad x center is used, and both are needed because, depending on the bike company, each is used. so to get the ball rolling:
let's start with what you're NOT. here is a detail from the
scott plasma prescriber.
you'll see that this bike - which is a fabulous bike but has a fit range that's on the rather narrow side, because of the (lack of massive) front end adjustability - doesn't present to you a fit solution. it's gauged to pad-center, so your pad x (ctr) of 425mm is not quite achievable on this bike. it's 20mm too long. you could do it. if you were a pro and you had to ride it, either the pads will ride 20mm further up your forearm or we'd fashion you a plate between the armrest cup and the cradle, or we'd drill some new holes in the cradle, or we'd choose a different cradle, something like that.
here's a detail from the EXTRA SMALL size of the trek speed concept. see how your 590/425 pad y/x numbers intersect at a solution?
you're a size XS, that's a "mid-far" stem, 35mm pedestal. do you want to know why there are about 8000 or 9000 posts on the speed concept owners thread? do you want to know why so many speed concepts were sold? and why so many were sold
on that thread? because this is how easy it is to find a speed concept solution on a bike that has an extremely adjustable front end. (carl matson, "carl" on the forum, formerly an engineer at trek, walked people through this many, many times on that owners thread).
here's the funny thing: there's not THAT much difference in the frame geometries of these two bikes above. it is the front end adjustability that makes one bike easy to fit and another not so easy.
we can use these pad x/y numbers of yours to fit you to any tri bike, pretty much, and that means either superbikes or mortal bikes (that take standard stems). can you either narrow down your list by brand or model, or by price range?
Dan Empfield
aka Slowman