13" = shish-ka-bob to me. Holy jeez that's an amazing feat of ability. I'd say you would be dissapointed by the feeldo. I think the it's around 6" with decent thickness. You could probably get something like it though. Maybe put a model together from a latex mold. Profit!
Well, in the interests of research, I just had another go with a "soft" dildo, and managed 14", but I don't know if that was because it was bending up inside me. After the first 6" or so, I can't really feel it any more inside me, just the delicious sensation of it coming and coming out of me! For the record, I could only get 8" or so in in "missionary", much easier in "cowboy" sitting up, best of all in "doggy" Kneeling forward, then it sailed up me no bother. NB, it's not as hard as an erect male penis, and quite thin, about 4.5"-5" around.
Good luck if you fancy trying it out! Only the first 6" of my ass felt it. I guess it's kinda similar for women? Maybe I'll ask. Start a new thread!