If you are using the standard bellows, there's no way you can focus a 65mm lens at infinity on a Sinar P, and I suspect not even with a recessed lensboard. You need a bag bellows or the ultrawide double bag bellows, and it wouldn't hurt to have a recessed board, and you should probably have both standards in front of the tripod mount. I don't have a recessed lensboard for my 65mm, and I think I've done it with the ultrawide bellows, but it's not a combination I use often.