any merit to the idea of changing a rods tip guide (without changing the rest of the guides) to the best available to increase sensitivity?

 

oe

No, the weight difference would be little, sensitivity difference unnoticable. Six 3 mm guides weight the same as one 6 mm guide, change them all the something lighter and your getting somewhere.

I agree with the above statement.  But will add that I always use premium ring materials for tiptops on rods I build to get the best chance of avoiding grooving.  I've never had a guide groove, but old cheapie tiptops have grooved.  I would not bother changing on an existing rod because it may never groove, and there is no problem waiting until it does.  Grooving does not damage line, unlike a cracked ring.

Not for sensitivity but for better treatment of the line and because a cheap guide will often groove from abrasion.  The tip guide is the one which ALWAYS and vigorously makes contact with the line.

Thought maybe better material might transmit vibration better.  I have changed stainless steel tip tops for ceramic rings.  Leader knots were getting caught on the stainless steel tip during retrieve.  Thanks for you opinions.

 

oe

As spoonplugger said change all the guides for a more sensitive rod.  I've done this to a couple of store bought rods.  I used minima guides in place of the stock heavy ones and it really works.