Without any ply lining above your head, just carpet you'll probably be just about OK. 'Just about' being the operative word Chip.
If this worries you, just find the nearest LDV hightop van for sale or go to your local commercial breakers and measure/find out what the height is like inside for yourself. Only that will give you as clear an indication as any if the headroom fits your requirements.
If it's not enough, just whack in an old fashioned caravan roof vent, the bigger the better for where you envisage you'll be doing most of your standing up in the back. That'll be the easiest solution.
If this worries you, just find the nearest LDV hightop van for sale or go to your local commercial breakers and measure/find out what the height is like inside for yourself. Only that will give you as clear an indication as any if the headroom fits your requirements.
If it's not enough, just whack in an old fashioned caravan roof vent, the bigger the better for where you envisage you'll be doing most of your standing up in the back. That'll be the easiest solution.