What's the best way to install bar extensions on XC?
Do the existing grips need to be cut away to accomodate the clamps on the extensions?
Concerned with crushing bar ends to clamp extensions down.
Also, are there any other issues with shifters and brake levers?

I tried a friends bike with extensions and found them very functional for climbing and hand position changes on long rides.
Thanks in advance

Bar ends - Yes you need to cut the grip. It depends on what bar it is, if its aluminum you shouldent have any problems crimping it. Alot of times installing bar ends makes everything more cramped....shifters, brakes. Good luck...

If it's a carbon bar, you do want to be careful... not only when you're snipping the ends off the grips but also with the clamp design of the barend and the amount of torque you apply. Many CF bar manufacturers have some tech docs to help you out with determining which clamp designs are compatible with their bars and possibly even proper torque values. You can also get some special anti-crimp plugs or reinforcement rings that slip inside the bar and prevent the clamp from crushing it when you tighten down the clamp.

I personally run my barends a little loose so that in the event of a crash, they will move instead of snapping off the tips of bar.

The best thing to do is to loosen your shifters and brake levers. Take a razor blade and slice off the very end of the grip. Or, if you've got an aluminum bar, hit the end of the grip with a rubber mallet. This will produce a cookie cutter effect on the grip. Insert a thin screw driver under the grip (careful not the scratch the bar) and spray some hairspray in there. Just enough to break the grip free so it can spin on the bar. Move everything inbound, enough space to mount the bar-end. Shift everything back outbound so the grip is fixed tightly between the shifter and the bar-end. Let hairspray dry overnight.

Oh yeah, don't go Gorilla Grip Tight on your shifters and bar-ends. You want them snug, but not tight, like Khuon said. If you crash, the bar-end or shifter or brake lever will spin instead of being so tight it breaks! You should have them tight enough that it'll take a fair amount of effort to turn them.

L8R

Here's another, possibly safer method:
Move everything inward. Loosen the shifters and brakes and move them inward the width of the bar end. Moving the grip is a bit mroe tricky. The earlier suppestion with hairspray is fine. Another method is using an air gun, but thatr requires the use of an air compressor. This method does not cramp things together as much, you just move everything over.

That's what I meant, but didn't say. Ooops!

Right after moving everything inbound, I should've said, Install bar-end and then snug grip and shifters outbound again!

I was thinking faster than I was typing!

L8R