This is a modified lead screw guide for use with the CNC front idler tensioner designed by Christian (https://github.com/EarthToMe/3D-Printer-Designs) which is available on Aliexpress (search on the Funssor shop). As the tensioner is designed for enclosed v-core 3.1, I have had to design a version of the front lead screw constraint to allow for use with a non-enclosed v-core 3.1. 

It requires that the front 3030 extrusion be moved down by 62mm akin to the OpenFront mod (there is a jig included that allows you to do this easily). This also has the added benefit of much better visibility of and access to the print-bed. 

You will not require any additional hardware for this mod. Everything (bearing, M6 screws and T-Nuts) can be reused from the existing lead screw constraints. 

Steps:

1. Print the parts (the lead screw constraint will need to be mirrored, and you will need to print two of the guides)
2. Remove the existing front idlers, lead screw constraints, and corner brackets.
3. Attach an M6 screw and T-Nut into the hole on each of the guides.
4. Insert the guides into the top of the front two upright 3030 extrusions. Then screw the 3030 extrusion which you removed into the two guides (see first and second pictures). Attach the corner bracket.
5. Remove the guide and attach the corner bracket. 
6. Fit the bearing, M6 screws and T-Nuts into the lead screw constraints. 
7. Slide the lead screw constraint from the top such that the top of the bearing is flush with the top of the lead screw. Tighten the M6 Nuts.
8. Attach the tensioner if you are using it. 
9. Done !