I must temper your optimism a bit though. The knee surgeon was very worried about the chondropathie of the knee disc. Because that is not solved by a knee replacement joint.
So I have to try to grind the backside of the kneecap as much as I can by myself. Byclicling is f.i. a recommended training; but it has to be done with care. It can worsening the kneedisc also. Twenty years ago I've made and designed my own recumbent bike from aluminium. It's a socalled low rider with a backseat that is ofcourse 100% modelled for me. Moreover It has also frontwheel suspension and backwheel suspension so its chockfree. Last week I mounted a chinese E-motor in my bracket with which I can control precisly the pedal force which I have to add.
See the motor upfront and the battery behind my head.
in our Catamaran sailing club we have these exUSSR inflatables aka Prostor (Простор), which is actually a copy of English inflatable catamaran Catapult. We modify and upgrade them for race and slightly higher wind conditions.
We sail and upgrade them mostly of "having fun in learning" purposes.
the original Prostor catamaran is quite a touristic or leisure sailboat this catamaran is easy to upgrade and most of it is DIY. The problem is that the more you upgrade the less it is easily transportable. We hold and store them in the club and transportation is not an issue for us. We only sail them inshore.
Good boat to start learning to sail a catamaran. Inexpensive. Easy to store in winter period. In sailing season we hold them outside so after every sailing it is necessary to deflate them almost a half, as the heat from the sun and caused higher pressure inside the hulls will explode them (experienced this once ).
For transportation purposes I would definitely go with modern of these days inflatables like Smartcat, Happycat or Ducky.