You might very well be pitching it a bit low.
Take the example of Virgin - they have taken delivery of 250 ULD's.
Trial order.
An A340 carries anywhere between 15/20 ULD.
Means you must have similar number at destination airport.
Each flight - every destination - and some spare ones - even if attrition rate is 25% of alloy ones - still means some degree of spare capacity required.
This product has a huge potential market place - which will be even greater when the Kelvin temperature-controlled boxes come on stream.
I think you may need to revise your sp projection - at least I hope so anyway !