I make my own bath butter base, whip it up and add 10% light oil, 5% FO and 150% sugar.
5% sounds high for FO, sorry, I know that's a bit off topic, but I noticed it. Edited: If you are calculating 5% FO without the sugar amount, then it's ok, mine below is 4% without the sugar amount.
I don't have my recipe using bath butter base handy - oh wait... maybe it's on my phone...
Yep, I do have it! My recipe includes the sugar as a percentage of the mix, but it's x2 the amount of only the bath base. I've added the % without the sugar included in ( )
Base 30% (76%)
sugar 60% (152%)
glycerin 5% (13%)
oil 3% (8%)
Fragrance 2% (4%)
This is very loose the day I whip it, but the following day will be stiff. If yours is still loose the next day, I would tweak the amount of oil and try using some glycerin. ETA: I think the glycerin helps stabilize the bath base when you whip it.