Oh no, its gonna have to be quite long isn't it?
My tug is 20" long by 6.5" beam. The men on it are 16mm/foot scale railway figures and seem to be about the right size. So its very roughly 1:19 scale.
What do you reckon – a 25m long lighter comes up at 1.3m at 1:19 – Gonna be HUGE!
Might have to draw the line at 1 metre otherwise getting plywood might be a bit of pain? See what Addlestone models have got.
Trevor explained about his false bottom barge which sounds like a good idea otherwise it will need so much ballast it will be unliftable!
Here's Bertha as of this afternoon when I walked down the river:

Not going to be around a few weeks which is a shame as would be fun to see an engagement between Nelson and Tirpitz!