Slow sequence

Hey there,

Recently I have been editing projects that are quite long, where the footage will go up to the hour mark in my sequence. I was wondering what could be making Premiere slow regarding its playback. When I play my sequence when fully rendered, it seems to struggle with playing and keeping the framerate up and I am unable to scrub and watch to edit which is making it difficult to have a good flow at the moment. 

The project is 338GB, in my footage folder, it is 20GB.  I have enough drive storage where this is being stored to handle, I have rendered my timeline, tried creating new sequences, disabling clips, soloing audio and lowering the quality playback but this hasn't made any improvement. 

I am working with Multi-Cam sequences. - Perhaps I could make my project into a bundle of sequences for every 10 minutes or so, making it less of a hassle to have all in one sequence which has worked before. 

I would be grateful for any suggestions if it is possible to have this fixed in a master sequence to run smoothly as my PC should handle this well. 

All the best.