I you can, I'd just do R&S 2 for 2nd this year and move into 3 with Bigger for 3rd, doing a lesson per day. OR even better would be to not worry with grammar right now and just do R&S 2 with Bigger in 3rd bc it's a gentle start but that gentle goes away quickly! It's a very advanced and rigorous grammar program. Finishing level 6 by the end of 8th grade is the goal, and is beyond what most public schools cover even in high school. You can award high school credit for levels 7+. So there's no rush! My son is starting Bigger next year in 3rd grade and will have had no grammar prior. Really I've seen no need for it and he'll pck it up easily being older when he first starts learning it. I waited a bit with my oldest too and she's 10yo and half way through level 4. It's getting quite challenging!! 5 is going to really step it up. She's retaining well and the retention improves as she does more writing through HOD bc grammar is not as pertinent unless you're writing. And 1st and 2nd graders don't do much writing usually.

that why we wait...if they use it, they'll learn it better! They've had no difficulties picking up grammar habig had a later start. If anything, it's easier to learn and it's not drsfert already bc they've not ears it over and over since kindy
So really, you can just wait until you start Bigger and do rod & staff as planned without consequence. But it is plenty easy enough to do 3 in its place by doing a lesson per day of grammar plans. Then in Lreparing and up, you'll have plans for more levels. Preparing has levels 3&4 planned in the guide, CTC has 4&5 (both half speed for balanced language arts/writing), RTR has the second half of 4&5 scheduled, Rev2Rev has half speed 5&6, etc.
There's much flexibility and you know your goals best. Here we tend to not really do level 2 and just jump in at 3, with Bigger or Preparing and have more or less done our own schedule with it just lesson by lesson bc that's what has worked for us. We will be on track for my oldest to start level 5 when starting CTC though so she can follow the plans herself from the guide each day.