The front uses the same length dogbone for the e/t maxxes; 57.5mm. There's a bit of play so you'll need to put one o-ring for each cup. 59mm would be the ideal length if you decide to have one made by RCalloy.
I can't see the picture from work.
Castle Neu 1520 on 6S LiPo Powered Gmaxx (Nitro Killer)
Predator with OS .21TM
Supermaxx with Mach .26
Revo with OS .18TZ
Kyosho ST-RR Conversion
Ofna CR with Tekin ESC/Motor (2)
Cool!! I have a few extra front stock length ti shafts.
Besides the O-rings you can also use some silicon fuel tubing to buffer the gap in each drive cup. It really does the trick and since you are still a nitro guy I am sure that you have some laying around. Good to see that you are having fun figuring this build out for BL. Have a good one.