Thanks Mike and Mark. I agree that backing off a bit will make longer sessions a bit easier however I do like to fish as light as possible. I take #5,6,7 floaters and s/t lines and rods with me and fish with the lightest that conditions allow. I find a marked difference between the #5 and #7 floaters with the same make and model of rod (10'), line and reel (Lamson Liquid, very light). Not a lot of difference in static weight but quite a significant difference over the day to my ageing body when casting. I'll consider a #5 SLXi when reviewing next seasons purchases.
I use the #6 green, longer bellied version in cross winds when bank fishing. It has a different casting action - smooth sweeping strokes. Not a line to punch out a lure but can be deadly with wets and nymphs.