Deecey has offered excellent advice, I will try to offer some but from another angle...sometimes seeing something from another viewpoint makes the picture become clearer.

Bones - Once they are created in the Setup room just leave them be. Editing or deleting bones can be left for later once you have the conforming item working correctly...so lets get that one first.

Import - With K4 Zeroed out does the Shirt import properly onto the stage fitting around K4 with no poke-throughs? For conforming to work correctly the Shirt should import perfectly fitting K4, if it doesn't then your base obj file is causing you some problems.

Setup Room - Use either the K4 figure or if there is a Developer Rig for K4 use that, also let Poser group your obj file as well as apply bones.

Copy the joints from K4 to your shirt and now try conforming it to K4. What happens?

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