They do have tuning kits that have those kinds of weight increments.
On my agility I went with the 5 gm sliders, but I did try 5.5 and 4.5. The Dr. Pulleys I've seen come in .5 gram weights so you might have an issue trying to get to 5.2gm sliders.
I ordered rollers that were 4gm, 5gm, and 6gm so I could test them out. I did mix weights - three 5 gm and three 6 gm to simulate the 5.5 gms. Mixing works fine for the short term to test as long as you alternate the weights to balance it out.
The lighter weights give it more punch at take off, but you lose acceleration as the speed increases. You have to test out the different weights and give them a week or so of driving in to know what will work best for you.
But I do like the sliders - they are smoother and don't cost more than quality rollers.