In article , MLenoch
wrote:

John, are you saying a stripped down civilian P-51 cannot pull up from
level flight into a vertical loop without first diving for additional
airspeed?

Yes........cruise speed in a Mustang is 240 mph and a loop is flown at 300
mph.
You can try it, but you'll be very ragged at the top. You might even fall
out!!

How many G pull is that?
Do you maintain a steady g throughout the pull?