Hi Ed:
For what it's worth, my traveler rail which appears to be the same original type/model as in your pic, does not use every hole to fasten. Here's a pic of my traveler and car to evidence its the same type as your original. But looking at my pic, I believe that the holes in my traveler are closer to 3" centers. I'll be at my boat tomorrow and will confirm. From the Owners' Manual specs, between my 36 and your 37, the mainsail has comparable square feet . If the Garhauer rail has only 6" centers, I would do your best to use every one as is their recommendation which would give the about same number of screws bolts as every other hole on our originals. Or if the Garhauer does has closer centers than 6" between holes, at least ascertain that the rail itself looks as thick/robust as our originals and won't bend with fewer fasteners than recommended. Hope that I have understood right!