After a few hundred miles of having to trim the front derailleur every time I put any torque on the drive train, it was time make a change. Whenever the frame flexed, the Shimano CX-70 front derailleur required trimming to keep the chain from rubbing the sides of the cage. The cage on the CX-70 seemed a bit narrow with the inside at 12 mm for the 8 speed chain, leaving very little clearance when using anything other than the middle cog of the 8 speed cassette. Rather than changing the chain, I went to the parts bin to see if I had an older double which would have been designed for a wider chain. I found a 1982 NOS Shimano 600 Abaresque with a cage that was 14.5 mm on the inside. The curvature of the 600 cage was very close to the CX-70 so I made the swap.
Shimano FD-6200, 600EX Arabesque
The 600 shifted as well as the CX-70 with no issues of the chain rubbing the cage. Problem solved....and the new old derailleur looks very nice with the Herse cranks.