Getting a perfect 90° cut on PTFE tubing is a royal pain in the .... yeah. If it's not perfect, you are just asking for leakage, which is NEVER good in any situation, especially in a 3d printer hotend. You could take the heatblock apart and trim the tubing flush against the metal sleeve, but that requires disassembling the hotend which isn't particularly fun, either. What you need is the PTFE Tubing Guillotine! Simply slide your tubing through the hole until it sits firmly inside to rear pocket and slice. Easy peasy.
You will need a 25mm (1") long 3mm bolt, a 3mm nut and two (at least) 6mm long 3mm bolts as well as a standard Stanley-type knife blade.
As requested, I have added another version of the base that has the PTFE tubing hole cut all the way through to aid in removal of the scrap piece. This is v3 of the base.
UPDATE PART 2
As requested. I have added another version of the base that has a 45° angle guide in addition to the straight through guide. This is the v4 of the base.
Due to either a Thingiverse bug or (more likely) shadowbanning, my models no longer show up under the [Newest] listings. If you want to see more of my models, please be sure to 'follow' me.
Another Sketchup Model - Debunking the Myth that Sketchup is Useless in 3D Printing
You can print the base with less infill if you like - 20% or 30% even, but the arm and the keeper really need to be 100%. It doesn't use much more filament and the additional print time is negligible. Rotate the arm and the keeper 90° so that they are laying flat on their backs to avoid the need for supports.