On the newer K3020 clone of these 40w laser's the back wall is farther forward and the X-End bracket will hit it before the homing switch is reached, also at the head the cable chain will come into contact with the back wall as well so i had to push the cable chain farther forward and shortened and modified the X-End bracket as well as the carriage mounting bracket.
The laser holder is made to fit a 12mmx30mm laser module, i used one with a cross pattern lense and after printing the laser holder it will be slightly undersized so i warmed up the part with a hot air gun and press fit the laser module into the holder. Alternatively you could file it out for a snug fit and use a bit of glue, i used a dab of hot glue once the focus on the laser modules lens was adjusted to keep it from rotating and going out of focus. I also modified the carriage mount for a single side mounted laser module, the original was setup to mount two laser modules for a cross dot setup but using the cross X-Lens version i didn't need that.
The Tab file is optional but if you want a Y-Axis cable chain then it gets glued to the side of the X-End mount, this was done in two parts just for easier printing and its plenty solid after being solvent welded to the other piece. The other end of the Y-Axis cable chain is just attached to the bottom of the cabinet with some double sided adhesive mounting tape as it doesn't take much if any movement stress. This gives a nice smooth running location for the air line and laser module power wiring.
I also modified the air tubing hole on the carriage mount to just pass the flexible silicone tubing i used for the air line, acts as a strain relief, and it loops down to the barbed fitting on the air assist nozzle. I used the air assist head from LightObject as its so cheap!! Just take note that these machines have a 12mm diameter focal lens and the LightObject air assist head uses a 18mm, but there is a design on here for an adapter ring so i printed one of those and re-used my 12mm stock lens and it works great!