My experience with a Worksman reversed cargo trike- it is more stable than a bicycle at slow/stopped speeds, but less stable at anything over maybe 8 mph. IE, unless you keep speeds really down, you don't necessarily gain the stability you'd expect. I expect this is similar with conventional adult trikes.
The tadpole trikes are generally really low. There are some recumbent trikes that sit higher, in between that and the upright-style; you might inquire in the Recumbent forum as to the options there. First question, I guess, is just exactly how high does a chair have to be for him to get out of it?
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