Ive found the commonly used 2/20 is very rarely required. I totally understand that it covers all bases, with regards speed especially.
For example, ive perfected test prop 100mgs/ml so it is virtually pain free.
For sterility issues we know that 0.9% BA kills 99.9% of bacteria in liquids. Hence the standard for bacteriostatic water being the same. Water harbours more bacteria than oil.
1.6/9 in MCT (Fractionated coconut oil)
I reckon that formula would hold your mix too, considering raw materials and chemical structures..