Spoilers within!

After some GM Burnout killed a homebrew campaign, I convinced my players to give RotR Anniversary Edition a try. To soften the blow of the previous campaign ending and respect the work they put in to new characters after the last session ended with half the party being killed, I'm letting them transfer their characters over at level 3. (Mechanically identical, but they'll need to tweak backstories a tad.)

I plan to use milestone leveling and don't want them to have to go all the way through the Catacombs of Wrath to level up, so I'll probably adjust the milestones as follows:

3rd: Start
4th: After Glassworks
5th: Finishing Thistletop (RotR recommends starting chapter 2 close to 5, so this isn't too far ahead.)
6th : As planned in adventure path

Do you think this will work? I know I will need to beef up encounters a little, early on. And it might limit the amount of side adventures I can do between Chapters 1 and 2, and I'm worried that'll feel too rushed.