Thanks ladies. I guess most would agree to start at 1a. I've used Singapore in the past so I'm somewhat familiar with it. I guess it's still best to begin at the beginning!
Unfortunately, I've loaned out some if my Beyond books, including the guide. A friend needed it for this year.
Would adding in the intensive practice or challenging word problems be wise since he loves math so much and 1a might be a tad easy for him? I'm over the academic pushing

and if I felt that would push him too much, I wouldn't consider it. He just wants more. He finishes what we are currently using which has several more problems per page and asks for more. If only this would last forever. Hahaha!
I may just get the HIG to add a bit for him. I'm not sure but I will be sure to start with 1a. Thanks everyone!