I attached my GL but bolting it right to the same support for the regular thompson front grip. I left it as in tact as I could and even used long bolts with the same thread pitch to use the same holes. I did reinforce the front with a brass 'strap' that was riveted in place to keep the lower bracket from sagging forward.
Hopefully this pic makes all that above make sense.
Test fitting
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Plan for longer bolts, washer and original front end bracket/holes
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modded piece
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Final fit-up
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