i'd have to say that you will need to be very critically cautious with any choice of upright delta (2 wheels in back) trike.
even the recumbent longwheel base units have a level of top steering and "crab walking" on off camber (sloped ) surfaces.
i might build a trike on eday but it will be a recumbent tadpole design (2 wheels in front) design.
there is a fantastic thread here on the forum showing just that kind of build by alaskavan. very well done and great pics and even some video.
bottom line : i would never be able to do 30mph on anything like what you have shown, and i have alot of fast motorcycle experience ie. hanging off the side with an knee on the pavement cornering type stuff.
BUT, maybe 30mph is optimstic on your part and you'll be going mostly straight ahead and turning at traffic light speeds ?
go over to the 'picture gallery" scroll down to "my next project - Tadpole Trike"
good luck,
steve