So remember, slider velocity is a multiplier of BPM. To keep sliders actually moving at the same speed, you need to adjust the slider velocity to balance old the new BPM. Here is the equation:
(1 symbolizes the old numbers and 2 symbolizes the new numbers)
BPM_1 * sv_1 = BPM_2 * sv_2
If you have more than 1 BPM, you will need inherited sections to balance this equation