how many ***** has your lot experienced? I seem to recall the tail clearance on the 400 was a bit less at F1.
It has been a long time since I flew the classics, but I seem to recall 10" on the 737-400???
We had a tailstrike on a -400 shortly after delivery of the first, with only scraped paint to show for it though. A tailstrike on landing produced some damage a few months later.
The tail clearance figures in the FCTM were changed shortly thereafter IIRC.