Honestly, the difference between a 5 or a 6 weight (or between an 8 or a 9) nowadays is actually less than the difference between a “5 weight” made by some manufacturers and a “5 weight” made by others.
I agrre with this statement but i have noticed that from rod company to rod company rod weight are very diferent.
I use to fish a #8 9.9 loomis GL3 and tried a Gatti Fr 3pa 10 ft #7 and the difference was very noticable in the weight and casting that I put that rod to rest (GL3).
Jocelin