Is this tripod study for long exposure shots? Also, it should handle a 5dm3 &amp; 17-40mm lens just fine, right?
Even though the Manfrotto BeFree Compact Tripod is considered a "travel tripod" meaning it is lighter, but may fit into your camera bag, I would definitely use it for long exposures with a 35mm. But it will be important to use a cable release on your camera to prevent any jarring. If you want to play is safe, a bean bag suspended between the legs of you tripod would make it extra sturdy.
I put my Manfrotto 234RC on a Manfrotto 3006 monopod. I used a 1/4" to 3/8" adapter, that cost me less than $2.00. The 234RC is 3/8", and my monopod is 1/4". I think these two sizes are probably the industry standard. Either way I don't think you would have a problem. Hope that helped. Mike