How many AGU's do I need?

[stephensmat]

I've only done one asteroid capture, and it was a small one. My next contact is a Class D. Assuming I manage to navigate right, do I need to worry about the grip I can get? I can mount 3 Advanced Grabbers on my craft, but does that have any advantage over just one?

[Curveball Anders]

One is enough, actually more than one is asking for trouble due to the way that crafts are structured in KSP.

Adding struts  via construction, auto-struts or (my favorite) EVA Struts is optional.

[Vanamonde]

Claw parts are tricky. Despite appearances, only one will actually be attached to the asteroid. The others will merely be objects which bump into the surface. You'd be better off only using one and then keeping the stresses you put on the joined craft low enough so as not to destroy anything. 

[FleshJeb]

I’ve used a single claw with landing legs arranged radially around it to brace. It’s been a few years, so I’m not sure if that’s still viable.