Hi DM Blake! It looks like the sheet is still set to display as NPC. I do not believe that drag and drop will change that. Try clicking the gear icon in upper right that appears on hover to put it into settings mode. You will see several options for display, including PC, NPC, and Vehicle. Switch the display to vehicle. Finally, when you drag "Ballista", are you dragging the monster or the weapon? The Vehicle Weapon is correct. Here is a screen shot of the character sheet in vehicle mode: