Essentially with para, as line line is being added, the rod feels just a little softer with each increment loading farther down the rod, so the energy stored in the top portion of the rod is still able to load the line, as well.
My load taper descriptions that I wrote for karstopo, and linked to, begin with progressive and compare how other tapers change from there.
viewtopic.php?p=338343#p338343The closest rods I know to pure para are the Para/metric 6'3", of course the Type Para Driggs River, Floyd's Guadalupe, and the graphite technical casting rods. Certainly Charles Ritz tapers, which were designed for casting tournaments fit in here as well.
Para is a casting tool to get the greatest possible line speed out of the rod length. Derived rod tapers deviate from a para starting point to make the rods more fishable. One direction they go is adding longer softer tip. Also adding a longer slightly stiffer portion to the butt - semi-para, which you can also get to by taking a wet-fly taper and making the tip faster - Heddon 8' cane tapers are Right Here, and the longer para/metrics - these rods excel at throwing big hardware.
But faster mid (than the tip) by definition is progressive taper - in a progressive taper, the mid is everything for loading in most fishing, you progressively gain a little more stifness down the rod as more line goes out, and the power curve will eventually run out. Look at it as a bandwidth of stored energy progressively moving down the rod with more line out.
You're still fishing out of the mid in a para, but there's more and more energy to store all the way to the butt, and when you do, the tip is still storing energy, as well - the bandwidth of energy keeps getting wider as you move it down the rod, and the tip is still working hard.
As I mentioned on the linked post, the soft tip and fast mid make progressive tapers forgiving. Wet fly tapers/ semi-para are forgiving.
Para tapers generally aren't forgiving, but reward good form with amazing casts.
Trev, yes, MOC is material of construction, but for rods, equate it to specific or equivalent modulus.