I had to file the sides of end links slightly to get them to fit, but once it slipped on it was a perfect snug fit against the back of the lugs. I polished the filed edges smooth to remove sharp angles that could scratch the lugs. I did not have to squeeze or stretch them at all. One tip though, I had to use slightly shorter pins than the ones used for the strap. The pins have to be able to compress flush with the end links in order to slide it on. The stock pins were too long and do not fit flush so I could not get one side of the pin into the hole because the end links have no give side to side.
If you are careful you will not have any marks on the back of the lugs from removing the pins to change between strap and bracelet. But I suspect after prolonged use of the bracelet you will eventually get some marks on the inside of the lugs (that are not visible externally while the bracelet is on) just from metal to metal contact between the end links and lugs.