Lou,

The additional filtration of Castor Oil should have been done at low temperatures, at low temps. there are higher molecular weight fractions that will crystallize out, these crystals could block small passages, and should be filtered out. The extreme pressure additives to Castor Oil that are added by Klotz and other brands of Castor Oil motorcycle lubricants are fully soluble in Methanol and will not effect needle valve settings.

RE: Weight/Volume. You are correct about the specif gravities, ALL BLENDING OF MODEL FUEL SHOULD BE BY VOLUME! Any company selling model fuel that blends by weight is pulling a SCAM. Model fuel blended by weight will be low in Nitromethane, low in Oil and high in Methanol. As Methanol is the lowest cost ingredient in model fuel you see what the vendor is trying to pull.

Ralph