I designed this support for my frame, an Anniversary Special Edition Martian 215 frame, however the dimensions should be compatible with a classic Martian II frame.
The viewing angle is 20 degrees.
I recommend using a volume to avoid creating support in the strap slot (for Slic3r users)
or simply enabling "support on build plate only", otherwise it becomes difficult to remove it. I use 16mm straps (16*250mm battery tie down strap).
Added the 25 degree version