I'm seeing delays in fills using my U account.

Number 1 reason why there are delays in your U account is because its getting its fills from an F account. This is an IB limitation with F accounts.

Since we do not receive fill notifications for F accounts there will be delays spanning from seconds to minutes.

Subscribers will fill according to what the strategy shows.

With non-allocated IB accounts (U accounts not linked to an F account), we receive fills in real time and the signal is sent to C2 immediately.