I guess the question I have is why you feel the need to reinforce the trans mount? It isn't exposed to the heat, vibration, or fuel spills that the engine mounts are. If your transmission isn't dumping oil all over the place, a good quality mount should last a decade or two easily.

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)