is there a shock that will drop the m2 to around 29" on the back.

Not sure about the exact height but there was an M2L produced, I believe the shocker and the front mount were different, whether any parts may be available is another matter, I think also the seat may have been different too.
It might be worth checking with AST suspension quite a few folks on here have used their shockers and have good reports

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Last year I joined a group for anti-social people
We haven't met yet.

M2L shock:

https://www.twinmotorcycles.nl/webshop/artikel.asp?mc=1&aid=8475

(looks like the standard pre recall shock, as currently fitted to my S1 )

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Martinwill of this parish has done as you wish to do. Maybe worth a PM...

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08 Specialized Langster

Yes, i had to lower my x1 due to my disability so i made an adjustable front shock mount. i'll dig out a photo if i can find it.

adjustable front mount