Thanks 11.4. I don't have much experience so I'm inclined to believe you, but I too would like an explanation of why this would be. The guy who originally told this to me had no good explanation, and no real anecdotes either.
Looked at from the other side however, if one wants an 87" gear, would it not then be inadvisable for one to run something like a 39x12? One could do it with an older road chainring (no pins and ramps) and a suntour 12T cog, on a 130BCD crank such as a stronglight. What is the drawback of going too small, or is there one?