I own a 8.5ft 5wt and it's a staple for my trout angling in streams. Don't go with a rod that is too stiff for trout, roll casting and single hand spey are pleasures you don't want to mess up with too much high tech stuff. I can also reach into a cast and get over 100' with it when needed. It's an old Sage RPL, closest equiv nowadays is the VPS (see sponsor site).
If you were fishing float tubes on big windy lakes it would be another story and you could go up or down in rod wt based on fish size as well as fly size but Nick has it right IMHO.
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