recommended level of BLUE silicon in Graham 1.5t/ceramic

jw, all the way up. Then check the resonance frequencies with a test record like the Hi Fi News Test Record. I think you'll have to add some weight. 
Next time you are inclined to upgrade get away from unipivot arms. Many manufacturers like Lyra recommend against them as they are not stable under all circumstance and a torsional resonance is added to the vertical and horizontal ones. This is particularly true for MC cartridges like yours because of their lower compliance. High compliance MM cartridges fair better but still. Aware of this problem but wedded to the unipivot design Graham developed an opposing magnet system to stabilize the arm which is certainly an improvement but I would prefer spending the money on good bearings. I particularly like Kuzma, SME, Reed and Origin Live arms.

Great cartridge by the way!!

What Mike said. From Graham to Origin Live was a great leap forward for me. The silicon fluid is nothing more than different viscosity. This same fluid is used in the shock absorbers on remote control cars where the viscosity is used to control shock damping and hence handling. Exact same stuff only without the pretty color and the pretty amazing markup. But really in the big picture you could go from one drop to max level high viz and as big a difference as that would be it'll be like nothing compared to going to an OL, Kuzma, etc.