Well, son of a gun! I had no idea about his medical condition and the "tail" actually hid the rest of his real body. You would think the production might have taken better advantage of that situation. As it appears, that tank looked like it was designed to hid e a body. One would think the prop cre could have made it more "open" to really drive home the point that's all there was to Sil's form. You think it was originally built with the intent to hide a normally proportioned actor, and afterwards they had the luck to hire Shaban?
Yes, I'll admit the second make-up design is far better blended around the face. Personally (and if the performer were willing), I would have applied some sort of "T" shape to make the nose and brow section a tad more "alien", sweeping the form into those frills, leaving his eyes, cheeks and lower face free to properly emote. But that's a "quibble".
Huh, all this time I just assumed it was a "body in a box" motif. Learn something new every day.