I have wanted to purchase an Arca Swiss style ballhead with a L bracket for my 5D but could never afford it.
My big issue with the manfrotto clamp and Quick Release plate was the size and it just seemed to be a bit wobbly when mounted with a 70-200 F/4 lens.
I kept my eye out on a couple photo forums and found an Arca Swiss clamp (photo clam brand) for $35 and I also found a Kirk BL-5D for $70 in LNIB condition.
I removed the old proprietary manfrotto clamp from my manfrotto 488rc4 ballhead and installed the arca clamp.
It was super easy.
The end result is a smaller setup with a tighter clamp, more versatility and L bracket compatibility.
**Check HERE for an assortment of arca style clamps.** (I am not sure if all are compatible with bogen heads)
Here you can see the massive difference in size between the two clamp/quick release systems.
My old Pentax ME was just a stand in for my 5D. When the L bracket is on the 5D it completely hugs the camera’s curves and becomes a part of the camera.
Here is an image from Kirk’s website that shows how the L bracket hugs the 5D and allows all the doors, flaps, etc.. to open.