I hate to get back on subject, but I too wonder what the best glide speed is for the planes I fly.
I usually use the default alt-x speed but sometimes I edit it with the .speed command and don't know what it is for sure. And when I need it most I want it to the nearest mph!
Now, for extending the glide when the engine is dead, use the Numpad "-" key - it makes a HUGE difference.
I discovered that the 190 can actually maintain alt & get home with no radiator by running at full throttle at best climb speed. When temp gets too high cut off engine, feather prop, & cool the engine. When it's cooled off , unfeather the prop "+" key and go to full power best climb speed again. Repeat as needed. I flew 40 miles with no radiator starting at 2k alt and almost overshot the landing!