1990 was a nasty recession and boats not selling. My boat built as a centre cockpit wheel steering detachable wooden canopy river cruiser on a narrowboat hull, intended for the Severn and connecting canals. I bought cheap as it was a one off , but knew I would have difficulty selling. Was living on board,needed storage for my tools and materials for working on my boat on the towpath and could not afford to pay for hotel if sold before bought something liveable. Very few widebeam builders and prices high. Imports of european barges dried up . Grand Union barred for widebeam north of Berkhamstead, but ok for narrowboat pairs. Widebeam drydock facilities few and expensive. Wanted to be able to cruise narrow canals and Europe. Quote for stretching my 60ft hull to 70 ft about 5 grand gov. Quote for approximate copy shell £9000. Buy the second boat and bolt them together was the best solution for me, and I have never regretted doing so.The hulls can be separated for drydocking and road transport.Would have gone to Europe through the tunnel. I have never had to separate them to get past an obstacle. However, my advice now would be to think about where you want to do your boating. . If you are ok being restricted to the North or South widebeam systems, then go widebeam. My main advice for widebeam is watch the tunnel and bridge profiles. The published headroom for canal bridges is taken at the centre of the arch, and is much less over the width of a maximum beam boat. I have met several people who bought barges in Holland and Belgium that were within the GU lock dimensions, and had an airdraught of less than the published maximum, but could not get past the first arched canal bridge they came to. The bridge and tunnel profiles is the reason why I welded guide wheels on my roof at the front. The profile of my boat was that the roof could hit the brickwork before the gunwales hit the timber, and the screeching of tortured 200 year old bricks was awful.