Duke,
Never had a problem with the umbrella valve being locked up on these regs. even with a new main diaphragm. I wouldn't alter the outflow valve. You will hear of duckbill lock up on US Divers and Voit Regs due to the duckbill valves tendency at rare times to geat reversed into the horn if a diver hasn't checked it after rinsing the reg. It happens rarely. That is why you always do a predive check to ensure the duckbil or unbrella valve is operating correctly and after the dive rinse, rinse, rinse in warm water and do a post dive check with air to the system after your reg dries out a bit. We need to do this to all regs regardless of type after a dive, but many people just dip it and hang it up without giving it the proper care a life support device deserves. I have been guilty of this on occasions in the distant past and it cost me some bucks to fix it.
On my recent reg. the 4th generation Siebe Heinke 1963, they ran into problems with duck bills being restricted due to the over sized diaphragm closing the duckbill. They fixed the problem intiially with a cross bar attachment in the top can on the 5th generation and finally redesigned the 6th generation to have a full restriction plate inside the reg. All I did was just replace the original high ceiling diaphragm with a new silicon US Divers one, works great. The British had a tendency to really over-engineer and over think stuff at that time.
In the case of your Healthways, you have an angled umbrella valve box. This allows the umbrella valve to flow regardless of diaphragm "Press" into the top can. The idea behind it is that with such an angled outflow "box" even if the diaphragm is pressing onto the valve, you will still be able to exhale due to that angular tilt of the umbrella valve box not allowing full restriction by the diaphragm and thus force the diaphragm back to its rest postion. It does not take much air on the exhale to do this at all. So to answer your question again, don't mess with the outflow box.
If you want to re-chrome the body, all I can say is find a well recommended chrome shop. I am over in Saudi Arabia and I have a guy down in Riyahd that does a fairly good job, but I don't think his quality is up to US and European standards. As far as the valve "spider" support. As long as there is good brass underneath the verdigrised and decayed chrome, you should be good to go. A good chrome job should fix this problems. A little light tweeking at the cross beams of the spider support is needed at times to ensure that the valve seals up well. Just play with it gently and tweek it lightly until you are satisfied, to wit; suck and blow into the exhaust horn. If it is pushed in, take a plastic or wood dowel or other stick like device and gently push up from the inside through the horn to get the spider more or less leveled up. Level the spider out as best you can BEFORE you send it into the Chrome shop. Just remember that Healthways did have nice chrome, but their can bodies and design were somewhat less robust and well fitting than a US Divers or Voit reg. So tell your Chrome guy to be careful when electro stripping the body to get rid of the old chrome, copper wash and such. In other words, this is not a 1957 Chevy bumper so your chrome guy needs to tone down the juice in his stripping vat. Remember that a good chrome job starts with really good cleaning of the item to be chromed and that item needs all of its old chrome and copper wash removed before a good re-chroming. JMO.
Here is a Youtube link that shows some of the regs I rebuilt a couple of years ago, to include a 1955 Healthways in action.
https://www.youtube.com/watch?v=JilzDSJ41DI
Russ