if you have 5-6inches x 5-6 inches per cola, probably okay... some personal preference involved here too... strain-related considerations etc.
same with reducing trimming. Strain will dictate alot of what you can do. Some will gladly grow nice tall stalks of fat buds, but others will bush out more. I'd guess that the bushy ones need more colas to optimize yield vs trimming work... and a more sativa, lanky bud pheno might do better with fewer colas.
Next run of my F#1 i'll do 6-7 colas... they'll be nice sativa-liek buds. The BBM/NOG plants might do better with 9-12 each. (15"x15" plants, 4 of them per run). These 3 grows are the basis of my thoughts lately... trial and error.