I'm confused can I buy a PCC for a J118 and my 510 batteries will fit? I have shaved off the buttons so that is not a problem for me. I just HATE the current 510 pcc and have been looking to make my own for the past three weeks. This would be so much easier!
Although the JSB line of PCC are similar in size, the depth of the connector is different based on the models. The one that would fit a 510 would be the J118 pcc as it sits lower than an L88.
The connector should fit a 510 but not sure if the positive leg will reach as their depth is different. Would need to widen the hole to fit the button as the 118 design is actual screw in and not push engaged like the 510 pcc.
It also wouldn't be difficult to take the inner compartment of the 510 pcc and just fabricate a wider casing/housing. Would need to mold an additional plastic container if you wanted to house an extra battery or 3-6ml bottle of juice.
There are moldable plastics you can use like shapelock.
Here are some pics of the inners of a 510 PCC, I am not sure what you wanted to add, if its another slot channel for an additional battery then its not possible unless you find a wider casing. If you wanted to ditch the extra slots for carts then you have a pretty decent area to work with and can fit a small juice bottle (light white area shows the room you have to add extra stuff if you dremel that area out)