Thank you very much, David,
Well, there goes another one of my theories!
I'd like to run a few other sentences by you before I close this chapter!
What do you think of:
c) It is pleasant for him drinking a can of beer after a long day's work.
d) It is dangerous for him swimming in the river.
e) It is a dangerous thing swimming in the river.
f) It is a pleasant thing drinking a can of beer after a long day's work.
My feeling is that only 'f' really works, but my feelings have proven very unreliable in this area. Needless to say this last post was prompted by your comments about the length of the predicate.