What is the best method for connecting 2 or 3 panelviews, to 5/03 unit, that perform well ? my last effort using net aic /rs232 to 3 panelviews is a bit slow and locks very occasionaly showing no active node on any one of the panelviews requiring a power down to cure

With a 5/03 you are stuck with serial communications, which by nature will be slow. You could try a scanner and RIO panelviews, but RIO panelviews are a pain in the a@@. In my opinion, best option is to upgrade to a 5/05 and use ethernet.

Or a method that will be slower than a 5/05 but will be a little more up to date would be to but a 1761-NET-ENI on channel 0 and put it on Ethernet

using ethernet hmis and 503+ENI might work but it will be slow (which might be acceptable, you get what you pay for).
there will be price difference for HMIs using different comm interface too, so it is worth
doing some math before spending money. ENIs are expensive and for price of 3-4 ENI modules
one can buy 505 processor

Very good point