Torsion Bar Recommendation Needed

[zen]

I would like to get some input on what size torsion bars I should go to. Currently my suspension is way too soft in the rear. The car is a bit too low currently and bottoms (and tops) out pretty easy. I would like to stiffen this up quite a bit without going radical.

Here is what I am currently running that impacts the decision to some extent:
'73 standard bug
Koni Reds
Late 944 ali arms
944 spring plates
17x8.5 Boxster rims
24 extra lbs. of a TIV
CSP Cup Brace

If I remember correctly, stock bars are 24mm. Do I go 26, 27, 28 or what? Any confirmation on length and splines is helpful too so I can order them before pulling mine apart. Anyone with the parts I need willing to give a GermanLook.com owner discount is always appreciated.