Obviously it's no sportscar, but my lovely Hercules is very stable to ride and on wet Winter roads and in muddy going I can feel confident that I'm not going to end up on my ear. When I first started to ride tricycles over a year ago now I was worried about the single wheel drive on the LHS, but it's never been a problem for me. However the biggest improvement between my first tricycle and the Hercules is having the hub motor wheel at the rear as well. The drive is much more balanced and traction is improved by having all the powered wheels at the back; - and with a 28inch wheel on the front I find that the steering is much better especially over bumpy going.
For a serious tricycle a traditional heavyweight lugged roadster frame with braced forks is the best choice. My Raleigh tricycle was built around a lighter 'sports' (English Racer) type frame and I had quite a few problems with bending and flexing. Though to be fair I will confess that I did cruelly overload my poor old Raleigh sometimes.