Hola dboy -
xxx
Used to fly LR-20/30 long ago, also 55 a few times.
I would wait for 20 feet AGL to start flare.
DO NOT CONTINUE FLARE until touchdown.
When "about to touch down" (2-3 feet AGL) relax your back pressure.
xxx
If the LR-60 has auto-spoilers, on very long runways, DISARM auto-spoilers.
Deploy spoilers manually after touchdowm. Expect some pitch-up with spoilers deploying.
Try that - and let us know...
Same technique I used (with different heights) from Lear to the 747...
Un conseil qui marche...!
xxx
Happy contrails