I just purchased my first spotting scope (Vanguard Endeavor HD 65) after reading many of the reviews here regarding entry level spotters. I have a Vanguard Alta 263ap tripod with a qs-51 quick shoe. My question for anyone that may have ran into this is that the quick shoe has a slot in the middle. The slot allows the scope to slide freely even after tightening fully. The bottom of scope appears to have a set of holes on either side of the bolt hole but the quick shoe has no male component to match. Any idea how to stop the sliding? Thanks for any help you can give me as I am less than 48 hours from a long drive to Montana for spring bear.