You most certainly have to reinforce or buy a replacement boltsled. Try something similar to Tantum Bull's longshot sled reinforcements (wire), or oznerf's sheet aluminium method. I actually do not know 100% if this method will work on the retaliator (since the clearance between the Darttooth guide thingys and boltsled are very limited), but it's worth a try. If you choose the safer path, then an aftermarket sled is sold by orangemodworks in their retaliator stage 2 kit.
Other then the boltsled, you should reinforce the back spring rest area. This can be done with epoxy putty, or machining your own metal spring rest (like the OMW one). I'd use the epoxy putty since it's easier. You just apply it on the plastic that supports the spring. Otherwise, the force of a 8kg spring will crack that plastic.
For the plunger assembly, pad the plunger and reinforce the plunger rod. Reinforcing the plunger rod can
be done by taking some small gauge steel wire, and epoxying them in the grooves of the rod. Plunger padding should be a rubber washer, or foam rubber. Foam will be destroyed under the force of that heavy of a spring.
Edited by Bubba Longshot, 02 June 2017 - 10:35 PM.
"The only thing that sucks about Nerf modification is the anxiety that something will break... That's why we reinforce a whole lot!" -Me