I used the 3d printed part as a quick drill guide as it didn't need masses of accuracy and it sped up the conversion a lot. I also decided to do away with the soldering iron handle as it didn't really need it. The last job I did was to modify one of the soldering iron tips by cutting a few mm off the end of the point. This meant that when fitting smaller thermal inserts the tip would fit inside the insert and self centre and could apply pressure without either poking through the underside of the insert or marking the plastic outside of the insert. It works very well and I may well may some different tips for different sizes.
Whilst the Dremel workstation inherently are a bit wonky and flexible (I'm thinking of a new experiment to try and make it a little better and some other mods, I'll post at some point) it's been great to use and the height adjustments it offers are great and it can accommodate a good range of work pieces such as this "MTV" robot... which I need to do a blogpost relating to in its own right!
Finally, below is a picture of an insert, It's great to be able to get these in well without marking the surrounding plastic and they work incredibly well and if put into the correct size/tolerance hole they are much much tougher than tapping into a 3d print.