This is due to the lack of load on the 12v line without the GDRom Drive installed...I have several Dreamcasts (my fave console of all time). The one with the GDEmu installed and stock PSU runs hot. It has twisted's tray too. Shocked me how hot it was when I opened the CD lid and a puff of hot air could be felt on my skin/face. My Dreamcast w/GDEmu will be spending much of its time in a cab. Heat is a concern for me. The spare I have for typical console use, ISO's and such, don't run as hot in comparison.
Just removing the 12v regulator should fix it...
Details here: https://www.reddit.com/r/dreamcast/comments/461ohk/how_to_remove_12v_from_dreamcast_for_gdemu_and/
@citrus3000psi can confirm?