Guys I've managed to get B9 working (along with several other mods including KW rockets and what not) with 0.90. Roverdude has uploaded a Hotfix for Firespitter, read over the last few posts on the Firespitter page to find the link and a few more details. Just install B9 as you normally would, then drag his hotfix in and overwrite. Haven't tested everything extensively yet but so far landing gear, engines, intakes, etc all seem to be working and animating. Make sure to give your thanks.