I have an M-10 on my 3541LS -- the "right" Markins head is the M-20 but the M-10 works fine. The tripod's base is a bit bigger than the base of the head but there is no issue. You save a bit of weight by going with the M-10 over the M-20 and currently you don't have any lenses that need the bigger head.
My plan was that if I never need more capacity on the head, it is easy to sell the Markins and move up but for now I'm saving some weight.
Thanks...I actually just asked the question about the head being a smaller diameter than the tripod base in another thread 
I was thinking about the M20 but I would like to save weight even if its like .25 lbs or w.e...
Also like you said none of my lens currently 'require' me to carry the extra heavy ballhead so Ill stick with the M10
Thanks again Hoff
you loose a lot more than an inch most of the time 



