Subsystems replaced with model references - simulation much slower!

Hello,

I recently took a 3-day Simulink training course. One of the covered topics was model referencing. I have a Simulink model in which I've been implementing subsystems in parallel, but were simply copies of one another. Whenever a change was made, all blocks would need to be updated. I updated the model to make use of model referencing. Unfortunately, it takes a much longer time for the model to begin running once the run button is clicked. Is this normal? I've tried both normal and accelerator options. The latter helps a little bit, but it takes substantially longer than when I just used subsystems in parallel.

Thanks for any guidance on this matter!