I only use the duramax blades rarely (spares) but when I have I feel they have plenty of bite... I'm leaning towards narrower rather than wider. My logic: I ran shoal cuts for most of last year, then went back to my regular dynelites (7") and I really like them better. One of the issues is in deep water the shoal cuts got too grabby. They're great in shallow water - but made the oars feel a lot longer in bigger water. I need to get another set of dynelites and am actually thinking of going with the 6"
Also quick calculations show that 8" carlisles are only 6 square inches larger than 7" duramax... going 8" with duramax would increase that to 240 sq inches (24 sq inches bigger than the carlisles). Personally I think that would be too much unless you run really short oars.
So long story short I'm with Andy and E-M.
"If you dont do it this year, you will be one year older when you do"