I have a 2001 Boxter S with 6 speed manual shift. Car has 41000 gentle miles on it.
At 70mph in 6th gear........how far down can I shift WITHOUT causing any damage?
I'm personnally thinking 4th. I haven't gone down any further than 5th.

 

I would think you could romp it into 3rd with the proper heel toe, but you probably better check what mph your redline is in 3rd gear.