I've done a lot of looking into seat heights as i have an embarrassingly short 27in inside leg. :'( it's not just seat height but look at width as well cos this makes just as much difference!
Also is getting both feet down at a standstill absolutely neccessary?? as long as i can get one down then i'm confident enough, you'd soon get used to it!
the only thing to do is to go and sit on/try as many machines as you can.