My home, built in 1931, was originally a coal fired two pipe steam
system. In the 70's the owner replaced coal with a weil mclain 76
series boiler. i believe my home has too many radiators (1500 sq ft
of steam edr) which is logical since energy was cheap and people slept
with windows open etc. On top of that, I believe my boiler is
oversized for the number of radiators I have. Originally my boiler
was fitted with a 4.25 gallon/hr nozzle. Now it is fitted with a 2.8
gph nozzle. right now i'm burning roughly 3000 galllons of oil per
year for a 4000 square foot house. Seems excessive to me. Even if I
reduce the size or amount my radiators wouldn't the existing piping
still require me to use a large boiler?

I'm thinking of switching to hot water but i understand that there are
pitfalls that need to be avoided. My radiators are connected at the
top and could be used for hot water. I would like to insulate my
house a little better and have a heat loss study performed before
switching to hot water so I can be sure that I have the proper size
boiler and correct number of radiators.

Does switching make sense? If so, does the large size of my steam
pipes eliminate the efficiency savings provided by a hot water
system. Could some sort of flexible plastic pipes be snaked through
my large steam pipes to neck them down ? That would also prevent
leakage problems.

Or an alternative would be to keep steam or a combinatio of steam on
my 2nd floor and hot water on the first since piping the first floor
would be easy from the basement.