There's always ways and means with a bit of bodgery - as long as there are exit holes big enough to get the end caps through (just over 1 inch diameter) it should work - may need some ingenuity to fix the clips for the tubes, but there'll be a way
EDIT: You can also boost the light further by fitting reflectors behind the tubes - Arcadia ones are easy to fit and work well on my 5ft.
CB3100 wrote: I was thinking about making my own with tin foil or mirrors? If that would work?
Yes it would - might be a little less efective than a pre-made one as they're shaped to provide the right spread while focussing the light somewhat towards the tank, but foil lining in the lid would definitely give it a boost.
Not so sure about mirrors though - foli would be easier to work with and safer (no glass!).