I found the thread and pictures.Go to;
Newmar Owner Forum
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Start the search , and read ( Slide Motor issue) when it comes up Check out the pictures in the post , I think you will find that his problem is similar to yours.
I would think , that considering the torque the gear case/motor produces to move the slide that doubling up on the mount would be a good idea.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.