Lvl Up golden Pound Usopp

Is it Usefull tol Level Up Golden Pound Usopp, he is still Lvl 27.

No he haven't a high stats so it isn't important level max Golden Usopp!!
But if you haven't another characters to level up then it is okay, so you can doing it only if you aren't waste your turtle ...

Theorie behind this is easy
1st: his stats are bad
2nd: he'll most likely not benefit from captains.
3rd: for both reasons it's likely you use him first to build up a streak, so he is not benefiting there either.

Take a Arlong-Slasher, Asura-Zoro Dex, Ace-Quick or Buugi-Int Team. In all those cases, his stats don't get boosted. So +10 atk equals +10 atk, while for other characters +10 means +40 or more.

Still I think, its fine to level him a little. Can't hurt

Eventually it will be useful even if only sometimes, since later on you might have survived a boss if you had only a few hp more and he does have a decent amount of HP difference from 27 to 50, but yea I wouldn't prioritize it over your main crew doing the damage

I think all usable characters should be leveled to at least 30 at this point. It mainly depends on how much xp each fodder gives you. If anything, at least he adds 1K HP to your pool, since he fits into almost any crew.

Elite alvida gave me a ton of Coby's, which gives 2.9K exp. The only other PSY characters I have are Mohji and Gaimon, who are both already above lvl30, so I just feed most 2-3K fodders to Usopp or just sell them. He's at lvl 44 now.