Cowl Panel Antenna Hole Size - more than 1 size??

[jocko]

Swapping from telescoping mast am radio antenna to a stock 72 fixed mast fm antenna. The fixed mast clamp and nut are shown.

Problem: What I'm pointing to is what goes under the cowl to clamp the whole enchilada together - but it's pretty much exactly the same size as the hole in cowl - i.e. it's too small. No way to "clamp" the cowl in between as this just pulls right through. I can rig up a way to make it work, perhaps with a fender washer, etc, but would much rather do this right.

Were there 2 different size holes in the cowl? (perhaps fixed mast antenna used a smaller hole?? Can't imagine that'd be the case).

Anyway - interested to hear if anyone knows. I've never had an am/fm in one of these before.

Or, if anyone has a bigger lower clamp/nut (the thing I'm pointing to, that won't slip thru the cowl hole.... I'm all ears).

Funny how it's always the "little" things that throw off the plan

Thanks guys!