heavy engine braking & cheetah VB

I just install a turbo action cheetah reverse manual valve body (PRN123) and I'm curious to when i need to shift or if there's something wrong here. drive in 1st is fine, as soon as I shift (i've been shifting a wide range of rpms from about 2500 to 4500rpm) into 2nd, it feels like it just wants to fall on it's face like theres tremendous engine braking. i haven't tried it into 3rd yet. Should i just try to keep the rpms really high in second? what does everyone usually shift at with the valve bodies? any suggestions? this is my 1st manual vb and am not used to shifting it, I just am worried and dont want to over-rev my new motor.