I'm fairly new to using Butter Rum. However, I found there is a very thin line between not enough and too much in a mix. So erring on the side of caution, I have determined my starting% for new mixes at 0.2% and work my way up from there. Well unless I want BR up front, then 0.5% to start. It's a deathly potent flavor but so good.
I think it more mixers would try LA Bavarian Cream, they would drop TPA's version like you and I have. There's no comparison really, and LA's version is just so rich and flavorful.