too big to nurse in a wrap?

I find wraps great for breastfeeding. As far as I'm concerned, size is not an issue. If both of you are comfortable, then go for it. Wraps are some of the best for being discreet because you can adjust pretty infinitely.

I nurse my almost 20 month old (26lbs or so) in an Ellaroo or a Storch.

oh that's great to hear. can you direct me to good instructions for how to wrap an older baby for nursing?

I usually do a front wrap cross carry or front wrap carry and just drop dd down farther for nursing, then pull her back up, bounce and retie when she's done.