Well, okay here we go.
I"ve flown it and offered what I remember from 30 years ago, you haven't flown it and offer what you heard from some guy.
I'll fess up and admit that I am that "some guy". I have flown, for a living not just a single flight, the Sabre 40/60, the Sabre 80 and the Sabre 65. I have have hand flown all of them from takeoff, climb, cruise at FL-450 and approach/landings. Of my 21,000 plus hours of flying time, over 3,000 of those hours are in Sabreliners. My last flight in a Sabre 40 was in 1984, last flight in a Sabre 65 was in 2005.
You are wrong about the aileron limitation of using more than one half aileron deflection above
any altitude. The only aileron limitation of the Sabre 40/60/80 is:
From page 1-16 of aircraft limitations in the Flight Safety International Sabre 40/60 pilot training manual, last updated 1982, paragraph H, Maneuvering Limitations;
DO NOT USE MORE THAN ONE-HALF AILERON DEFLECTION ABOVE
225 KNOTS.
This limitation was not, repeat not, due to any structural concerns of the airframe. The FAA added this limitation due to the fear of the FAA that the rapid roll rate of the Sabreliner 40 was too rapid for the average civilian pilot at any airspeed above 225 knots*. The FAA decided that the risk of loss of control could result from a full aileron deflection at any speed above 225 knots, resulting in possible lost of control of the aircraft.
The Sabre 65 has no such restriction.
I will now state for the record; the Sabre 40/60/80/65 are very delightful to being hand flown, regardless of altitude (including FL-450), airspeed and in any configuration.
Only two other aircraft that I have flown that can equal that statement, any and all Falcons and the Lockheed Jetstar (-8 and the 731).
Therefore, in my opinion, a highly experienced opinion, any pilot that struggles to hand fly a Sabre 40, at any altitude or airspeed is either a very poor pilot, a very inexperienced pilot or has never done so.
Your choice to make.
Oh, edited to add.
The US Navy bought a number of Sabre 40s from the open market a few years ago. Then these 40s were flown to Perryville, MO to be completely overhauled and modified to Navy specs. One of the modification was the additions of small vortex generators on the wing in front of the ailerons, to increase the roll rate at full aileron deflection, at any speed under VNE, to increase the already impressive roll rate. These Sabre 40s are now T-39Ds.
* Which means that a FAA test pilot scared himself during the certification flights of the Sabre 40.