If you use 100% VG out of the bottle of humco or now foods - you're going to have problems. If you mean adding a nic base and some flavoring then you're not 100% VG - even then any VG used for blending for a DIY that includes adding nic base and flavoring, should be diluted with either distilled water or pure grain alcohol with an 15 to 20 percent that with 85 to 80 percent VG. With that formula, it brings the viscosity down to around PG levels and should
vape well in a carto - I've done it without problems - I just prefer
tanks now with no filler.