Well, I for one have thought of  this issue in the past and just
recently and would like to know more about this device.

First your questions.

While I support using them for economy reasons, the engine stays in a
rich mode a long time, and this applies to all engines, with a thermostat.

I  feel that the agressive nature of the waterpump, indicates that the
engine should be driven gently, say 2000 Rpm or below until some
clamping force via the head studs is present. Especially on cold soaks
and cold wx.  So the worst cas senario I 'm thinking is a engine that is
quickly up to operating RPM on a cold morning, hardened jacket seals; a
large differnce in the expansion/ contraction of aluminum water jackets
and steel cylinder and head studs; and the waterpump trying to push all
of that coolant to the front of the van but the thermostat is
restricting this. Result higher than average pressure on the Jacket
seals, and less than average clamping force on the Head/ Jacket seals
via the steel head studs. So an opertunity to push coolant beneath the
jacket seals.

My questions is that I have several , 4 I think, old thermstats .  Some
have a large baffle or end plate and some have a smaller one.  Which is
correct.  Are these thermostats used in different applications.

Mark