A number of years ago Ken Smith showed me a really nice way to connect a Struble hound to the mast fitting using an aircraft bolt, castle nut, and safety pin.
I've used it for a number of years, and it works great.
You can get the parts from any aircraft hardware supplier (Wicks, Aircraft Spruce, AirParts, or even E-Bay).
You need an AN4-10 bolt (1/4-28 x 1" long, an AN310-4 castle nut, and a AN416-1 safety pin).
The big advantage of aircraft bolts is that they come in 1/8" length increments, so the un-threaded part of the bolt is only 1/16" shorter than the width of the hound, so the connection is as strong as possible.
If you want to get all three in a convenient package,
I have them available for $6.50+shipping.