My clinic recommended 3 days of bed rest (including the day of transfer). I was told to just maintain less than 45% angle (meaning head is less than 45% inclined from the body) and that any position was find - belly, side, back, etc.
That said, many have referenced research articles showing that bed rest has not be proven to be of any benefit with implantation.
So, bottom line, I wouldn't worry at all about it. Try to relax and think positive thoughts (I know, easier said than done some times....but keep your mind busy with other things if you can.....)
Best of luck to you!