Here's the install manual I downloaded to look at:
http://shop.easternmarine.com/index.cfm?fuseaction=home.getFile&prodID=6793
Page 4 has a way to test I believe would work for you. By the exploded parts view on page 11 it looks relatively simple with no real calibration. More like the harder the trailer surges against the hitch, the harder the piston inside is pushed and the harder the brakes are applied. So I would think you'd be fine as long as it's full of oil, hooked up right, and no air in the lines.
To me, since surge brakes normally don't stop the trailer by themselves (short of the emergency disconnect) they'll help just by applying whatever brake force they can. Do the m101 units you have come with an emergency disconnect that locks the brakes?
As long as you can just bolt/weld the surge brake to the new tongue without disassembling it I would think everything would be set up right.
Then again, my only real experience with them is on U-Haul auto transports towing near or over the max cap of my truck. My truck's rather light so pulsing the brakes helped slow down by giving the surge brake that little extra jolt to kick in a little more. So take that for what it's worth.