I've never tried Madagascar Vanilla, but it seems to say it's the same thing (
http://www.flavourart.co.uk/sweet-flavours-10ml.html) I also haven't tried butterscotch at high concentrations, but my feeling is that almost everything is bad over 8% max.
With regards to UC Steeping - I really don't know. As I said, things are weird if the day after, and change vastly over time. My completely unproven belief is that UC does a good job of mixing, but doesn't necessarily speed chemical reaction. Again, there's thousands of pages of UC knowledge on this forum, so they probably know more than I do. I should add that I have a little Amazon UC rigged up to run continuously. It's NOT a powerful transducer, so that may affect my results.
Grimm's Vanilla Custard is a favorite at my shop, which is really weird to me as well. Tastes like VC1 and Dulce de Leche. I don't get many other notes there (btw I said this before, but my setup across the board is .5 ohm dual micros - kanthal - organic cotton , across multiple TOBH clones).
I've also been trying to work with FA stuff a lot more lately as I feel like I've read that it's "safe to vape". Can anyone confirm this?