Converting 5 lb of Vienna malt to extract/partial mash?

I'm converting a recipe from all grain to partial mash. Speciality grain bill is at 2 lb right now, and I still have 5lbs of vienna malt to take care of, on top of that.

I've got some questions:

* What would people recommend as an extract (or blend of extracts) substitute for Vienna malt?

* How big would people recommend going for a partial mash? I assume throwing all the Vienna in the mash bag for a total of 7 lbs would be too much. Hence, I'm thinking of steeping 2.5 of the vienna (4.5lb total steeping) and substituting the rest for extract.

* Do I have to worry about steeping being less efficient than the traditional all-grain mash/sparge? Should I be adding some percentage extra when taking the all grain weights and putting them in the partial mash bag to be steeped?

Thanks!

Unfortunately, I can't think of a good substitue for Vienna in extra form. There are plenty of Munich extracts, but not much for Vienna. What is your recipe?

Actually, Weyermann seems to have one called "Vienna Red" but I don't see any US sources.

I'm looking to make a Flander's Red; it's Jamil's Rodenbach clone:

31.0 4.50 lbs. Pilsener
34.5 5.00 lbs. Vienna Malt
3.4 0.50 lbs. Aromatic Malt
20.7 3.00 lbs. Munich Malt
3.4 0.50 lbs. CaraMunich Malt
3.4 0.50 lbs. Special B Malt
3.4 0.50 lbs. Wheat Malt

Click to expand...

http://beerdujour.com/Recipes/Jamil/The_Jamil_Show_-_Flanders_Red_Ale.html

Bump, in case someone else is able to assist with some of my questions in the original post.

If your equipment can fit it just do the 7lb grain bill