The first part of DIY is here, using CHUG Jhiaxus to fill the empty back in gorilla mode. (Although it's more like a fan mode since no need to mod at all).
http://www.cybertron.ca/boards/showthread.php?t=73845
Now the 2nd part, which is a real small DIY, to use the Jhiaxus backpack in robot mode as well, plus give the small robot a gorilla mode.
1) un-pin here to separate the small primal, so I can give it a beast mode, and use Jhiaxus as backpack for Optimal.
2) Found junk part for gorilla and feet. I made Gorilla head and feet can be attached and remove anytime.
3) Drilled 2 small holes at the knees, so the feet can be attached in both beast mode and robot mode
4) installed the head and feet, here is the small gorilla mode.
And robot mode's back, gorilla's head is like a hoodie now, those feet can used to cover the hollow thighs.
5) Time to update Jhiaxus. Just pull the land gears out from Jhiaxus. Then those 2 holes can be click on optimal's back, as shown in the red circles.
6) Backpack view
Final result
Of course, all three parts can still be combined and used in gorilla skating mode.
