ok so its rugged but simple solution for the problem that i could not find any normal shifter base for my race sim 

MAIN PRINT INSTRUCTIONS 

1. use tough plastic types PLA may be not enough ( i used ASA) 

2.  3 wall min ( i used 4 )

3. infill 30% min

ASSEMBLY 

1.  use all the pre made inserts holes and assemble them 

(you should have 4 of them on "box1" and another 4 on “box2”) 

2. "box1" use 4 m5 screws with nuts  and washers to connect it to ur seat 

(should drill the holes before )

3. then assemble “box1” with “box2” using more screws 

4. and at last connect "box3" to "box 2" with the same method 

from my usage its holds firm but it mostly depends on ur print settings and assembly