No experience of kayaking but lots of experience with strictures. Was your recent operation for a stricture issue. I did recover my continence after dilatations and bladder neck incisions sometimes it was a few days other times it took a few weeks.
Are you kayaking in wet or dry suits. With elasticated waist bottoms I can quickly swap a pad, while walking, not as easy if sat down. With the conveen system I did get some 250 ml active bags.
Cold weather can be an issue when our bits shrink, the insides of the sheaths can stick together and the urine comes out of the opening of the sheath not the spout.Getting the correct size and length is key too success. Ugo will probably send you samples if you ask, the conveen Optima has the advantage of coming in a compact storage case.