If the little pinks you have are about 2.5g each, then 2 of them is about 5g. I think that's plenty for a 20g snake. That's 25% of its weight.
The Munson plan is a good rough guide, but it doesn't work for all snakes (some will refuse the bigger meals if you try to move them up sooner than they want to). And it certainly doesn't hurt to deviate from it a little bit, at least in the direction of feeding a little less. Some people feel the Munson plan is a little aggressive and recommend feeding a little less anyway.
The worst thing you could do is give too much in one feeding and cause a regurge. It is much better to feed a little less and have a little slower growth.