Do I need a double head on an Alaskan Mill?

[Rockwell]

Hello All,

 I am planning on slabbing multiple species of Central American hardwood (eg. Guanacaste, Honduran Rosewood, Granadillo, etc.). My choice of equipment will be an Alaskan Mill and my question relates to how much power I really need at different widths. Will I need a double head setup? I am sure that around the 3 foot mark it's not particularly necessary but being that the MS880 comes with a 59" bar, should I use 1 head to slab lumber of that width?

When slabbing logs that are 4-6' in width, at what point does having a double head a must?

 
Also, MS880 or 3120XP?

 
Thank you

Larry