Usopp skillbook

Will the 'Golden Pound' Usopp book drop on Kuro's veteran stage and the Sogeking one on the Elite, or is it just random across all three difficulties?

Cheers

Well let's look at Alvida event. The zoro book should only come out of veteran, but I find it in elite all the time along with chopper book.

it is random because i founded chopper and zoro book in the last stage ( the most difficult stage ) of alvida

But the official blog says:
"While unconfirmed, it is extremely likely that Sogeking books will make an appearance in Expert Mode (30-Stamina). For those that evolved their Usopp all the way, may this book find its way into your hands."

played on elite and veteran level over thirty times but there was no skillbook drop for me.
did anyone get some gp usopp skillbooks?

I´ve got like 4 gp usopp skillbooks from 15 Stamina (Elite Version) but the droprate for me was very very low.... luckily with x2 skill rate it was enough to get the last two levels.

in two weeks i was only able to farm 15 skillbooks i hope 
im lucky and can max out my gp usopp for the doflamingo raid