Here are some of my personal observations and opinions:
The Speedstar springs do indeed have higher pressure, but don’t allow for any additional lift. So, they’re great for stock or Speedstar cams. And also for higher compression setups, that might suck the valves open a bit on the intake stroke, with weaker springs (I don’t know that for sure, but read it somewhere.) But wouldn’t work for Orient Express or Patrick Racing cams since they’re higher lift. ( See my correction a few posts down, after receiving Gilly’s comment)
The OEM springs look pretty safe with the Speedstar cams, given their modest increase in lift. Maybe some risk of float at sustained very high operation, but I doubt it. I have been running who knows how many miles with Orient Express springs that are broken on the inners, with no float. Which, means they had dramatically LESS pressure than stock springs. Maybe think twice with higher compression, but that wouldn’t break anything.
The orient Express springs fit poorly, in my opinion. The diameters are too big for the stock retainers. In my opinion again, that’s why the inners broke. They DO allow much higher lift than either type of yamaha spring, but fairly negligible increase in pressure. They were cheap to buy, expensive to fix the problem after.
I don’t have measurements of the Patrick Racing springs. I’d bet they fixed the problem of fit, by including appropriate retainers. I waited 5 months, and could never get them. Ended up with some NOS Speedstars. So, my 110 ci, Speedstar cam’d bike lives to ride another day.