Willie,

Hey, I've lost two Silva Rangers to bubbles going from here to 13,000 - 14,000+ ft. One was well used and had made many trips well above those elevations over the years - no idea why it developed the bubble, but most of the time afield it was hung around my neck under my shirt rather than in a pouch or pocket. The 2nd one didn't even survive one trip. The one I now have is doing great. I *suspect* that these failed ones were invisibly "damaged" by getting squeezed/crushed thus allowing a minute crack to develop and have taken more care with the latest one - well, a little more care, anyway. Or maybe it was just lack of QC <shrug> who knows?

If you DO get a big bubble in the field, you may decide to drill two small holes into the capsule with your SAK and drain out the fluid - the compass needle will take longer to stop moving but it will be accurate. I wouldn't worry about your compass capsule for this trip if I were you - you'll do fine.

Tom