I'm an otherwise average guy with something of a curse: a very thick and rather long shlong.  My two questions are:

!) what's the best way to vet providers in advance who can handle it?  I've tried taller and older gals, but that doesn't seem to make a difference.  To be fair, all the wonderful ladies I've seen have been champs, and tried to go, but it has not always been easy to find a rhythm.  Nearly all the gals have been able to satisfy me orally (and that's been great!), but intercourse -- not so much...  BTW, I always bring magnums (which helps) -- should I be alerting the woman sixe-wise in advance as well? And if so, how?

and...

2) Am I destined to be an greek virgin?  Thusfar all the ladies who offer greek as a regular menu item have said no...  I'm very curious to try it.  

Anything should I look for in reviews and websites to help me out?

Thanks....

Seriously,  most guys would love to have your problems.  I can't offer any suggestions other than try the provider shown in the link provided below.  I am sure she will be able to handle you (lol)

That will give you some idea.  Second, PM guys who've reviewed her.  Finally, do not ask the provider in advance about any sexual service, as that will probably end the date.  However, once the date is made you can discretely ask her by e-mail if she's comfortable discussing "a certain sexual issue you have."  If she says "yes," then you can be direct.
I have a similar issue and have been able to find a few ladies who are willing to tackle it.  If you persist, you'll find someone who will, too.