Thanks relyt. I suspect you are right; I just don't want to have to redo the bike fit (read: buy a new stem) if I find that whatever I do is not suitable.

Another thought occurred to me, and that is that I could possibly cut a bit off the small (non-clamping) ends of the Ergon grips so that they would fit on the trekking bars. I'm just not sure if there would still be enough left for me to benifit from the grip though. From the clamp on the shifter to the bend in the trekking bars I have no more than 112mm (4 3/8").

Oh, and the bar ends on the Ergon grips can rotate independently of the grip, so I don't think that's a problem, I just wonder if that little bar end is really enough to grip on to. That and there is no way that the bar end model will fit on the trekking bars.