how to tell if a tire has nice stretched profile?

i searched here but again i don't know what search term to use.

is there a way of telling from a tire brand's sidewall design whether it will stretch well or not? what should i be looking at? bead protector? tread design? etc?

The only way to tell is by really trying it.  Some tires have larger section widths than others in the same technical size.

For example, an FK-451 stretches very well from what I've heard, but is larger than other tires in the same size, so plan to undersize if using FK-451/452's.

I also believe dunlop SP9000's stretch well (if I recall correctly).  As well as Yokohama ES100's. 

Tread design doesn't necessarily seem to be a factor, but actual tire construction does.

A bead protector will make the tire 'seem' wider, so for a more stretched look you will have to go narrower if you have a bead protector on the tire.

Make sense?

trying it means buying it, because everyone here has to special order.

Yes, trying it does mean buying it.  And if you dont like the choice then attempting to resell at a loss.

That's the only way to find out for yourself.  Look at some people's wheel and tire set-ups and you should find a good stretching tire in the desired size you want

Best thing to do is a search for "stretch" in the photo gallery or wheels forums and see what pics come up with wheel/tire specs.

Do you mean physically easier to stretch or aesthetically looks better stretched? I've read on this board that certain brands/models are harder to stretch onto a wheel than others.  I don't have much experience with that though, so...

As far as looks, I guess thats more subjective. The Euro guys really love Toyo T1-Rs for some reason. Personally, I like tires that are a bit more squared off, i.e. yoko es100 or jdm trampios or dunlop sp. I think tires with really rounded off tread shoulders tend to look like donuts. These are all generalities though, since it really comes down to the severity of the stretch and/or tire profile. 

In the end though,  I think it's just best to get decent tires that give just enough clearance to slam and drive your car. If your fenders are super flush with you rims, tire profile shouldn't be a major part of  the overall appearance, IMO. You sorta only notice tire profile when either the the wheel gap is too much or you have fatty profiles like 45 or 50 on smaller diameter wheels.