Hi Ron,
Before you cut any holes, unscrew one of the screws holding your current traveler on, and check to see if it is a wood screw long enough to go through the traveler, the deck and into a wooden cross beam.
When I replaced my traveler a couple of years ago mine was screwed on with stainless wood screws which I reused on the new traveler. So I did not have to cut any inspection ports. I did put sealer into the holes before screwing the screws in and I think I had to drill holes in some new places.
My thinking is that if its been good enough for 50 years should be good enough for a few more. Obviously check to make sure the wood beam is not rotten. My new traveler has held up since I renewed it and have sailed in some heavy air.
Jonathan
Questar 1226