If Xizor passes a hit or crit to another ship, and suffers no damage, does he still count as being hit, and therefore lose Stealth Device?

Yes.

If Xizor passes a hit or crit to another ship, and suffers no damage, does he still count as being hit, and therefore lose Stealth Device?

Xizor's ability triggers after step 6 but before step 7. So you compare results to establish if there are any uncancelled hits or crit results. If there are, then he has been hit, and that doesn't change even if he can pass damage on to a friendly ship to suffer the damage. And Stealth Device only requires that the defender has been hit in order to be stripped away.

If Xizor passes a hit or crit to another ship, and suffers no damage, does he still count as being hit, and therefore lose Stealth Device?

Let me simplify this for you even more.

"If Lt. Blount shoots at a ship with a Stealth Device does it lose the SD even when he rolls two blanks?" The answer there is "yes" because Blount's attack always hits. In other cases you'll still need to determine if a ship is 'hit' or not but if it is then that is that even if it somehow has something else suffer the results or can immediately get rid of them.

A tangential question:

Fielding both Xizor and Guri with Bodyguard, and intending to keep them in formation, if I have one stealth device and one Autothrusters, which upgrade is best for which pilot?

A tangential question:

Fielding both Xizor and Guri with Bodyguard, and intending to keep them in formation, if I have one stealth device and one Autothrusters, which upgrade is best for which pilot?

I'd put the SD on Guri. Her ability allows you to assign a focus token if you're at Range 1 of an enemy ship, then spend it to boost Xizor's agility.

End result: Both ships on AGL4, until Guri gets hit.

A tangential question:

Fielding both Xizor and Guri with Bodyguard, and intending to keep them in formation, if I have one stealth device and one Autothrusters, which upgrade is best for which pilot?

I'd put the SD on Guri. Her ability allows you to assign a focus token if you're at Range 1 of an enemy ship, then spend it to boost Xizor's agility.

End result: Both ships on AGL4, until Guri gets hit.

That was my thinking at first too. But I gamed it out against Brobots with HLCs and had them focus fire in Guri as the lynchpin. SD was gone on the first attack thanks to green blanks, and she was down to 1 hull after the second shot. So I swapped AT back to her (and gave her back two hull to continue my play testing). She still wilted. I'm Probably just proving to myself the extravagant expense of named Starviper pilots.

Quite a possibility. There's been a few StarVipers purchased in our area and I suspect it was for the Autothrusters card only, because I have yet to see one on the table.

The other thing of course is you can always make a "dream combo", but if you roll blank dice, nothing can help there. I had a game on Sunday where I took Keyan with Opportunist, Gunner and HLC against a Decimator at range 1. I declared the attack, to which my opponent said he had a Rebel Captive on board. More good news for me. Thanked him for the stress token then rolled 1 hit and 4 blanks. Gunner kicked in and I rolled 4 more blanks. The dice gods are fickle that way.

Quite a possibility. There's been a few StarVipers purchased in our area and I suspect it was for the Autothrusters card only, because I have yet to see one on the table.

The other thing of course is you can always make a "dream combo", but if you roll blank dice, nothing can help there. I had a game on Sunday where I took Keyan with Opportunist, Gunner and HLC against a Decimator at range 1. I declared the attack, to which my opponent said he had a Rebel Captive on board. More good news for me. Thanked him for the stress token then rolled 1 hit and 4 blanks. Gunner kicked in and I rolled 4 more blanks. The dice gods are fickle that way.

#Error

Rebel Captive gives stress when you declare the target. So you couldn't use Opportunist on the first attack as you would already be stressed. You could use it on the second attack.

Yeah, I guess that one slid past us. I targeted the Decimator, figured out I had 5 dice, and that's when my opponent remembered about the Rebel Captive. I guess we were both too amused that his Rebel Captive had backfired when Keyan attacked the Decimator first, that we just didn't think about the stress knocking a die off. Knowing my luck it would have been the one that rolled the solitary hit!