Where exactly do they draw the line (within the marriage)?
Specific positions? Petting? Sexy lingerie? What exactly is it about oral sex that makes it perverted? Can JWs have sex in the shower? Should they ask the elders first? Perhaps it depends on the size of the shower cabinet? Small cabinets may invite "unorthodox" positions? What about in a tub?
I think the safest thing would be to ask the BOE home with you so they could personally check out everything you do within your marriage. Just to make sure. After all - your everlasting life is at stake here.