jgf, if you haven't yet done it, it would be a good idea to read the Flight Notes on both these aeroplanes in the Learning Centre.
The key issue is that all those early aeroplanes were ridiculously under-powered by today's standards. This meant that they flew very slowly, and could only climb at what, by any sort of modern standards, was an 'imperceptible' rate.
The net result is that the Vimy, for instance (the one I know best) only had a cruising speed of 60mph, and could only climb at a rate of 1,000 feet per HOUR........

The Jenny didn't perform much better. And both aeroplanes appear to have been accurately modelled in FS......
What's more, even though 'trim' appears in the key-list, neither model, as far as I know, has trim control. The reason again appears to be 'accurate modelling' - the 'trim tab' had not been invented when these aeroplanes were designed!
I once had the idea of trying to re-enact the first trans-Atlantic flight (Alcock and Brown in a Vimy in 1919). I didn't manage to complete it because flying the thing was just TOO difficult and time-consuming - it left me with huge respect for Captain John Alcock, who hand-flew the thing on instruments, in ice and fog, for over 16 hours.......