Just a quick update for anyone that cares.
Seems the clam is doing very well. Foot is firmly attached to rock, and everyday he has had nice mantle extension, and both siphons look great.
On a great note, I think, I believe he is releasing excess zooxanthellae as the past few days I've noticed a long, brown hair like strand conning direct from his outbound siphon. I can only hope this is a sign that my lighting and par is more than sufficient if this is "excess" zooxanthellae that he doesn't need.
Overall I'm very happy with this addition to my tank. Looking forward to watching him grow. I guess you can say say he and I, well, we're both happy as a clam.