Yes although I've always understood that you want a slight load (1/2 to 1 degree of perfect parallel) on the U-joints, not neutral.

1" travel on the slipyoke should be optimum, 1.5" is probably neither here nor there.

1949 Chevrolet 3/4 Ton - Still Solid. Regular Driver
OT Vehicles:
1925 Hudson Brougham Super Six
1950 Chevrolet Styline (Parts)
1952 Canuck Pontiac Sedan Delivery (Well Underway)
1973 F250 4x4 Highboy
1977 F250 4x4 Lowboy