Nasal spray solution (volumetric dosing) can indeed be more exact than these gemstone or letter scales from off eBay. Sometimes I would get the same sample varying more than 20mg when it cames to low amounts.It sounds like you need to order a milligram scale!
Also protect the nasal mucosa a bit when made correctly. Downside is that with a nasal spray the redose is always just one hub away - this led to overdoses with me and ethylphenidate.
But I'm interested in the differences between various pyrrovalerones because I loved prolintane and to some degree its beta-ketone cousin a-PVP and consider buying some of some out of these currently available derivates. An adrenergic comedown like with x-MMC would be a no-no for me. Remember my heart racing like never before.