Fine white pharmaceutical grade lactose monohydrate powder or any other water soluble placebo diludant.
Take a plastic bag cut it into circle of about 20cm in diameter, put wet speed paste( up to 100g )straight out of the freezer in the middle of plastic bag circle. Add upp to 2g of lactose powder for every gram of paste, close the bag over it and use zip ties to seal it instead of tieing a knot. Then you knead it for 5-10 minutes until fully emulsified and evenly mixed. At first it might seem like it's too dry but the more you massage it the more it will start to be runny.
Place in freezer for 1 hr Remove from freezer and use a silicone spatula to fully remove all cut paste and put it straight into an airtight glass jar and into the freezer .
Bag it up all at once. Picture is of 5g paste cut this way.
Never use active cutting agents cause that's fucked up and sleazy.
Don't cut your speed! You can tell people to take Tropoflavin and CBD along with their speed to make it safer, but you can't cut your speed! Tropoflavin is neuroprotective and CBD reduces anxiety.
I would not use lactose, because many people get diarrhoea (lactose intolerant).
If you wont sell pure amph, i recommend for example,
1kg pasta, 500g caffeine, 500g Creatine.
Ratio can be up and downscaled, but it is a good solution, nobody will get too much health issues.