I’m only a measly 6’3″ but found the back protector on 661 armour left my lower back completely exposed.
The newer designs might be better but I went to a Dainese Pro shop and tried a few jackets on – they even offered to mix and match back protector and suit size to find the best fit (I’m tall but skinny). They are a bit more expensive but if it doesn’t fit properly it’s not worth anything.
Also with Dainese you might find a snowboard/MX is a better fit and are all pretty similar.
Generally I prefer to keep the jacket in one piece as I’ve seen plenty of crashes where separate arm/leg protection rotates or slides along a limb and leaves exposed flesh to slide along the ground. Are you likely to ever ride in a jacket but no arm protection?