Congrats on the L1!


Did you do your cert on the I140?
I would suggest you fly that rocket and your others on H & I motors and try a I284W or I600R before jumping into L2. That will give you a good feel for the range of power available in L1. When get to that I284 or I600, you will be near what a baby J will do in your rocket.
Once you've done that, you can make an informed decision on whether you want to try a L2 with those rockets or build a bigger, heavier, 54mm MMT rocket for your L2 attempt. You can still adapt down and use a 38mm baby J for the cert flight, but then you'll have a rocket you fly big Js, Ks, and baby Ls in.
BTW, a 4 lbs. 38mm minimum diameter rocket should get to about 6,900 ft. with a I600 motor from sea level, about 100 ft. more than a J350W would get per ThurstCurve sims. If you keep it down to 3 lbs. and use a J350W or J420R, you should get over 8,300 ft.
Whatever path you decide to walk, have fun!