My old Speer #8 manual does not show Unique with the 148gr
bullet.
My oldest Lyman list 3.5grs of Unique as the lowest data with
the lighter lead bullets.

In my 2" snub J frame;
3.5grs of CFE Pistol powder did 605 fps.
590fps is my cut off in the short barrel to prevent squibs.

3.5grs with a much slower powder may be asking for problems.
A "Starting load" of SR 4756 in my revolver had a low of 558fps !!
One reason to not go below a starting load until proven to be safe
in your weapons.

I would play it safe and pull those loads.