Isn't Grendizer's feet round, like bowls? For their round shape
you could try using a round plastic food bowl, or a pit ball
cut in half, close to the size of the feet, and use that as a
mock prototype to sculpt the feet with Durham's water putty.
Making one putty foot will suffice and will not make any
difference as either Left or Right foot...
Prepare your putty with hot water for fast cure, stir it
to a thick creamy consistency, and pour it into the bowl all the way
to the top of the bowl, and let it fully cure 72 hours.
...after the putty-made foot has fully cured
rock-hardin 72 hours, carefully remove it from the bowl,
then sand it and paint it with a coat of acrylic to seal it smooth...
...Then proceed to coat it with a release agent and use it in a
silicone mold to cast an authentic Grendizer foot with the
same material used for making repro Jumbo limb parts.
Be sure to make an Extension*** at the top of the foot above
the ankle ring for the following step..............
...after the foot is cast and cured, cut the original foot
(above the ankle) off of the jumbo's leg where the foot meets
the bottom of the lower leg-- you will see a gap there,
that gap is the ankle ring where you wanna sever the old foot.....
***Now... take the new "Grendizer foot" which you've cast,
and place it so that the Extension will slip up inside
the opening at the bottom of the lower leg.
BadaBING! ...new custom Grendizer foot!
Each of Grendizer's lower legs also have four red
vertical "fins" that run from the knee ring down to
the ankle ring above his feet.
You can grab an old jumbo Dragun or Gaiking lower leg to make
a mock prototype, and glue (epoxy) the red fins: one in front,
one in the rear, and the other two fins go on the sides
of the lower leg (as in North, South, East, and West).
Cast the mock prototype to make an authentic Grendizer lower leg
with an open bottom to slip the new foot into...
...or, you can use the legs you have there, and just epoxy
the red fins onto those legs you have there.
The fins, of course, can be painted red to match the red parts
on the rest of that jumbo.
Hope this helps and/or gives you more ideas.
(
late edit: Your Grendizer there is looking beautiful!)zozo-mag