I never bought the infant insert and I put DS in it tonight (facing inward) and he didn't seem all that comfortable. I kept his legs in b/c he seemed even more uncomfortable w/ them being hanging. I asked my sitter, who is BIG into BW'ing (she has several carriers and knows a lot about it), and she said he should be big enough w/o the insert, but I don't know. WDYT?
FWIW, DS is over 13 lbs and 24.5".
Re: XP: When to use Ergo w/o the insert?
Ergo says between 4-5 months. DD is five months, 16lbs, 26in, and we are still more comfortable just pulling the pillow out of the insert to use as a "booster seat." But she's been legs out for about two months now.
ETA: like several posts below say, you can use a blanket or towel rolled up in place of the h2h insert.