1. Connection between FG and -V

Connecting FG terminal and an output -V terminal don't cause any problem in the operation of a power supply. However, if you do so, specifications regarding withstand voltage between secondary side and FG as well as primary and secondary sides will not be satisfied. Doing so also turns insulation between primary and secondary sides into basic insulation and that doesn't meet safety standards.

Fig.1 Connecting FG Terminal with -V Terminal

2. Influence of eliminating secondary ground capacitor

If a ground capacitor on the secondary side is eliminated, electrical potential (output voltage) on the secondary side may become unstable. It will also increase output common mode noise. Therefore, please evaluate carefully before eliminating the ground capacitor on the secondary side.

Fig.2 Eliminating a ground Capacitor on the Secondary Side