As for my cath, it actually only has the one bulb, the one that sits in the bladder - for me that seems to hold it in place. This may be because the cath is actually pretty long - the end is only an inch or two from the end of my penis, and the draining holes only an inch from the end - but as the nerves all seem to be right at the head of the penis I still know when I'm peeing.
I've now reinserted the cath, without the string and it's much more comfortable - and I'm experiencing the incontinence I've always wanted; sometimes a vague dribble, sometimes something more, totally unpredictable, totally uncontrollable. I don't know how long it will work for - as I said before, a long ride on the bike moved it out, and I suspect it's something to do with a firm seat and riding position. Anyway, I'll let you know how I get on - for now I feel a pretty constant drip :-)