Cut up a softdrink can so you have a nice thin sheet of aluminium good for making shims. Cut a piece the shape of the flat section of the tuttle head side and check the fit. If it is nice stick it to the head with superglue or loctite. If it is loose try 2 sheets and so on...

Find an old can of spray paint and give the base as many coats as it needs to make it a tight fit.

Shims are a pain in the arse if you want to remove it and they will get lost etc so why not just do it right?

Rough it up good with about 80 grade sandpaper.
Scrub goodly with acetone or metho. This is important for good adhesion as you will have a very thin layer of resin at the end and you don't want it coming off too easily.

Paint on a good thick layer of fibreglass (polyester) resin or epoxy resin on just the sides (one side at a time).

When well cured, sand the sides back with a sanding block until it will sit in the box and and be about 0.5 - 1mm proud of the board. Screw tension will pull it in the rest of the way.

Cost - about $10 and 30mins all up.

Paint is not much good as it wears off too fast