Yes, definitely. Luffy may seem very 'what you see is what you get' but when it comes to anything beyond hunger, excitement and anger, it's tricky to write for - he's visual, expresses things physically, so he can be more tricky to capture in words. I worry about writing for Usopp too, just because I can imagine his inner monologue being a wonderful mix of crazy and really beautiful imagery, and it's not easy for me to get that right.