Any question answered...

How much fitness do you think you can build in 4 weeks?

Realistically, a little bit more than what I have now.

How much harm do you think you can do to your sickly organism in 4 weeks?

You could get some fitness but if you drill yourself and you fall apart before you even get there...

Oh, loads and loads. But there's a balance between sitting on my arse, and completely destroying myself. I haven't really got the right kind of personality for the latter. I've definitely got the right personality for the former.

And by riding I assume you mean in a social context as opposed to racing or even training, in which case the bunch should regroup at the top of any climb and ride at the pace of the slowest rider. Or, just go out solo.

I'm always fat and slow so they'd be doing that anyway, the gullible fules. I'd like some degree of comfort while I'm at it, though.

(I am arguing with you but I am taking your advice to take it easy at the same time I swear)