Nah.

If you know how to pack light (and you will learn...) 22" is plenty of room. I was able to pack enough for 5 RSV days in mine, but I only bring a couple uniform shirts, one pair of pants, and maybe 2 changes of 'civilian clothes' on a trip, along with all the essentials.

I know a few people who use the bigger PNT bag; it also fits in the overheads but I'm not sure about under the seats. Unless you're gonna be gone for 6 days, I'd say pass on the extra expense & weight.