Indeed, you can shim the scope base and get some more elevation. Shims made for this are available through Sinclair and others.
As Jeff noted, however, they misalign the scope rings to greater degrees as thicker shims are used. They are meant to be used with special ring inserts commonly used in benchrest shooting (another sport of mine) to relieve this misalignment. Using shims with standard solid tactical rings would put stress on the scopes body and action to varying degrees dependant on the thickness of the shim, of course.
A much better solution is to contact tactical base makers and have a base with greater taper custom made for you.
(I'll bet this whole line of thought is a moot point though, considering the vast majority of .308's will make 1K with a generously-elevating tactical type scope and 20 MOA base. Like I said, I have the same scope on a FLAT base and I'm only three MOA short of 1K.)