I actually avoid twinks cause there are so many out there. Suprised to hear you did badly with bears. I do pretty well with that as well as military. My top converting niches are:
facials
mature
bears
ebony
I'd say stay away from twinks. Oh and you didnt ask for sponsor but I do well with these niches at top bucks
Shelmal
I know I should leave my referal link but I dont want to spam