This all turns on what you mean by "challenge."
If the idea is to keep scores high, hell let me place the pins at 6500 yard Pasatiempo and I can guarantee an over-par winning score. It's all about how evil one wants to make a setup... and Pasatiempo surely isn't alone in this. Grow the rough high, speed up the greens to crazy stimps, make them concrete, the boys would be "challenged."
It would also be pretty stupid as they'd never hit a club longer than a 3-hybrid. And that goes for pretty much any shorter course.
So if you mean challenge every part of the game - driver, fairway woods, all irons, along with short game - sadly it is gonna take more than 7500 yards.
That is UNLESS you simply don't care what the winning score is. But then again, if the pros blister Dornoch for a score of 265 or something over 72 holes, were they really "challenged"?
I'd say one can argue they were regardless of score... but it's always going to be a tough sell.