I start gkrellm with
gkrellm -geometry +0-0
and I get the following warning in ~/.xsession-errors with FVWM:
[fvwm][GetWindowSizeHints]: <<WARNING>> The application window (id 0x1400003)
"gkrellm" has broken size hints (inconsistent with current size).
fvwm is ignoring those hints. hint override = 0, flags = 230
min_width = 156, min_height = 736, max_width = 156, max_height = 736
width_inc = 0, height_inc = 0
min_aspect = 0/0, max_aspect = 0/0
base_width = 0, base_height = 0
win_gravity = 1