When I modify a mold I put the hook where I want it, hold it in place with a piece of masking tape, put the mold in a vice and squeeze it as hard as i can. Sometimes a Dremel is not even needed.
I block all unused sections with RTV silicone.
Easy just lay the hook you want to use on the open mold lining it up with the hook eye and cavity . with a sharp pencil or fine sharpie trace around both sides of the hook making an outline of the hook .Using a dremil tool with a small ball tipped cutter start grinding out aluminum about 1/2 the diameter of the hook wire . Check depth every so often by placing the hook in the slot you're cutting so you don't cut too deep . When happy do the same to the other half . Make sure the mold closes fully with a hook when you're done or you will have a flashing of lead around the parting line between mold halves . You can fill or block off parks of a mold you don't want such a skirt collars with JB weld or red automotive High Temp silicone .
I got the 6 inch right as it was released and have had blast with it. I have had a couple of really good bites on it in a highly pressured public pond that is HARD to catch fish in. I poured it in a medium plastic and it gives it great action. I will see if I can post a video of the action for you tomorrow after I go to the pond.
Edit: Found video on my phone of swimming action on 8/0 Owners Beast Flashy
Swim Action Angling A.I. Swimbait
Tried to add a picture but the system won't let me.
Pm me your email and I'll send you some pics.
There's no need for plexiglass with a flat cap.
The cap is made to seal off the end of the pipe.
You want the flat cap so it sits level unlike a domed type cap.
The fluid bed cup seals off the only opening.
Other than the hole you made to mount your air valve of course.