The problem is you cant make it so that you only place psstones when you sneak.
You can however do the other way around, but thats not what I want. I want everyone to have "ps on", but i want them to sneak to place the psstones blocks, since they place them as regukar blocks more often than they place them as psstones which just makes it unpractical.
This is how my config looks, it should not be able to place psstones while standing normally, but able to do that when sneaking, but it is not:
settings:
prevent-place-everywhere: false
prevent-destroy-everywhere: false
sneak-to-place-normal-block: false
sneak-to-place-field: true
show-debug-info: false
show-default-welcome-farewell-messages: true
dynmap-flags-disabled-by-default: true
welcome-farewell-disabled-by-default: true
disable-ground-info: false
auto-download-vault: false
global-field-limit: 1000000
no-refund-for-fields: false
off-by-default: false
log-to-hawkeye: false
lines-per-page: 12
disable-bypass-alerts-for-admins: false
disable-alerts-for-admins: true
public-block-details: false
blacklisted-worlds:

• creative_world
  drop-on-delete: true
  version: 9.0

fixed in 9.1.3