I usually get 1 extra flavor shot when ordering MBV because I get their
juice at 50/50 and I find it needs just a smidge more flavor. Lately, I've been getting 5 extra shots at 100 PG and at 36mg and cutting with my own VG.
Only thing with MBV flavorings is they can taste a little perfumy at higher levels. Maybe you want to get 0 or 1 flavor shots at your preferred ratios but only get 15ml until you can figure out what you like / don't like about it and adjust from there.
When you get their
juice, I highly recommend leaving the caps off for a day or two to get rid of that alcohol / perfume smell. Then recap them and leave them aside for a good few days. MBV juices get much better over time when the flavorings have had time to mix properly. In fact, if you can wait a few months, they often change color (get darker) and become quite excellent.