Fleshwarped Scorpion's Tail
 

Is there a way to attach the tail instead of using only the handheld version?

I found https://forums.wolflair.com/showthread.php?t=60074 asking the same thing, but no answer was provided, and I'm not seeing an option to do so in HL.

The answer appears to be "no". You could copy it in the editor and make a "attached" version. You'd need a bit of scripting to calculate the new poison DC.