Tamron 90mm tripod ring to externally mount a flash

[Sylar]

HI all
I just got my Tamron 90mm 2.8f macro lens for my canon, upon unboxing it i noticed that the Canon version dose not have the aperture scale near the EF mount but it dose however have a recess, i got my trusty vernier callipers out and measured this recess to be 66.5mm across.
I was wondering if somebody may have already fitted a tripod ring to a Tammy 90 or if someone knows of a tripod ring that may do the job?
What i would like to do is mount a flash bracket to the tripod ring leaving the camera body less cluttered and more compact.

[Speedway]

1. the area you wish to mount the ring is too close to the camera body and it would foul on the onboard flash projection.
2. the 70-200 canon mount comes close at about 65mm but is too wide at about 17mm you would need a max width of 13mm.
3. you would possibly cause damage to the lens when tightening it onto the raised red mounting indicator.
A better idea would be get a ring flash or led ring light.