Deck Squat Progressions

I have progressed to Full/Deck Squats (PE3) in the F1 course and have a question regarding further progression. From a strength perspective, I have no problem completing repetitions, however, I have been using a strap recently to facilitate keeping myself upright (and not rounding my spine). My lower body mobility is fairly inflexible (I am using all 3 stretch courses which has been extremely helpful), and without the strap, doing a full deck squat puts a lot of strain on my lower back.

Is it recommended I stay at PE3 (or some other level) until I have the mobility to do the squats without a strap? Any other suggestions are greatly appreciated.

Hi Matthew, do not worry to much for the spine for now, your body it is made to handle this form, the only solution you have to reduce the rounded back it is to lean forward with the knees.