Hi @MSMDG,
I have had to do something very similar where volume accuracy on a rather large volume was of utmost importance. The goal here is to minimize any type of factor that could add to the “random walk” effect of volumes dispensed as you progress through the plate with the same tips.
I would start with a new and unique liquid class for this step where many of the parameters are zeroed out - air transport volume, blowout volume, over-aspirate volume all set to 0 to minimize cumulative inaccuracies from consecutive aspirate and dispense steps.
Stick with 300µL tips since the bore is smaller than that of 1000µL tips and the air gap (which is compressible) above the liquid and below the plunger is smaller. Aspirate a first aliquot of greater volume than you need - if you need 200µLs in the plate then aspirate 220µLs. Then dispense 200µLs back into the reservoir, effectively pre-wetting the tip while leaving a small amount still in the tip.
Now perform your aliquots to the target plate using a fixed height with no liquid following. Pick a height where the 200µLs will end up submerging the end of the tip just a bit.
I’d say all other liquid class parameters can be generally optimized for your convenience. Don’t set flow rates super fast to add to inaccuracy and not too slow making the protocol take super long. Then adjust your correction curve to make the volume as accurate as possible.
Matt