In order to make this mount work you will need four 1" Clamp collars. I buy them from McMaster-Carr. I've searched high and low for a better price, even going direct to the manufacturer but McMaster-Carr is literally selling these at about 5% over their cost.
I generally use the 316SS version but the 303/304 version will work too IF brightly polished. The 303/304 collars run about $17.00 each and the 316SS run about $32.00 each.
Either collar type will greatly benefit from polishing. They come in a mill finish which will show rust spots if not polished bright...
NOTE: McMaster-Carr links are odd and your back button may not work once you get there.. Bookmark this page before you click the links below.
1" Clamp Collar - 303/304 Stainless PN# 6436K38 (LINK)
1" Clamp Collar - 316 Stainless PN# 9633T19 (LINK)
NOTE: Clamp collars are always purchased based on the tube, pipe or shaft OD. So a 1" pedestal guard gets 1" clamp collars or a 1" prop shaft would also get a 1" clamp collar.
Here the four collars are shown mid-buffing...
To install the mounting plate set your bottom collar height first. Now using some long nose pliers, preferably with electrical tape on the jaws, press the top and bottom collars together while tightening the set screws. This makes for a nice stiff mount that does not wobble.