UL spey really is a niche all its own - not light enough to be a true ultra light - but not heavy enough to be a true spey rod.

I too fish a "Decho" in 4wt and love it! I find it to be an absolutely fantastic tool for hunting Cutthroat trout - both on rivers and off the beach - and for all the reasons specified by Joby.

Its requires very little room behind the caster to throw descent line, mends the drift as easily as thinking about it (the Decho 4wt has a length of 11'9''), and because I mostly fish streamers for larger Cuts, the "down and across swing" suits the tactic - and the spey cast - very, very nicely.

I like heads and tips for spey - so I rigged up the Decho with a Airflow compact scandi head @ 300gr ( on an Airflow Rdgeline running line) and fish it with the Airflow trout-weight poly leaders (floating, hover, intermediate, slow sink, fast sink, extra fast). The rig balances very nicely.

The added bonus is that if I happen to tangle up with a Steelhead, the rod can handle it without unduly stressing the fish (Steelies on my favorite local system occasionally run over the 18# mark) - something a 3wt or 4wt single hand just can't do in a Vancouver Island winter river flow. When the Steel run starts to show up, I switch up to a 9wt spey, as I think that only fair to the fish.