Tank Track, Double Idler, Arms, Beams

These are what I ended up with for Idler Arms for the tank project. Double idlers and buggy shocks. Used buggy shocks with ball end and drilled hole for 6-32 bolt to go through arm.
These use the Tank Track, Idlers, spacers to complete the set in my things.
Tank Dbl Arm ML-R are for the middle, Tank Dbl Arm SL-R are shorter for the rear. Tank Dbl Arm Beam is the beam to hold Idler wheels for these arms. L and R are for left and right sides. Tank Dbl Arm FL-R are for the front and go with Tank Dbl Arm Beam FL-R. These have an extra spring on the beam to keep tension on the track as it comes off the track Idler wheel.
All of these Idler Arms take the same 1/4"x1/2" Shoulder bolts as single arms at frame pivot point.
When I made these I just happened to have some Kirby Vacuum cleaner #174091 Cord Hook Swivel bolts laying around that work great for the beam pivots. Threaded them all the way down and cut bolt off to fit. Since these may be expensive to buy, included a Tank Dbl Arm Pin that will take their place. Not sure how they will hold up compared to metal. Use 4x1/4" sheet metal screw and flat washer in pin to hold in place. Drill pin with .093" (#42) drill bit for screw hole.
There is a YouTube videos of the Tank with Traxxas dual Velineon brushless motors and dual 3S Lipo batteries.

Updated drill guide PDF added. This is a work in progress please check for updates.

Update: Thanks to fellow Thingiverse tank builder that shared these shocks that work with some slight modifications to the suspension arms. The shocks I used where for a HPI Brama 18B #103003 and #103004. The HPI shocks are about $100 for 8 shocks and the following are about $30 for 8 shocks on ebay, "WLtoys A959 Vortex Complete Oil Filled Front and Rear Shock Absorber Set, Parts List #'s A949-55, Fits all versions of the A959 vehicle".