I had memorised pi1000 three times with different combinations when i was younger.
The first time, I memorise pi was too green(unskillful ) in memory field. I use pure 2-digits object system. I connected them into two objects per locus. Soon, I used up my loci around 50. I had only remember 200 pi-digits with many gaps bc of poor planning and review.
The second time I was up to retry pi-1000 about a year passed. I had also written a learning journey. Start-up a new exercise routine on number system!
That time I was ambitious, bc I had built a visual APP to aid my revision and learning. With PAOX, I can bundle up 8 digits with minimum repetition.However, I was naive! I cannot hold the objects tight, though the visual APP does a great aid. When I reached around 500 digits, my mind already knotted. I don’t want to recall pi anymore bc I did mistake on here and there, just like you have a old house 
. You want to repair it, but holes happens in everywhere one after another. 
About half year ago, my revision edit PAO is almost done, I wanted to try my system. And I remembered Pi the failed challenge, it was a great chance to conquer pi1000. This time my route are carefully planned, my visual App is still there, and most importantly I have better sense in mnemonics! I was shocked that I can use PAO to learn first pi200 on the first day!!! I thought it’s bc my previous pi experience gave me power. Then I continue my learning progress and turn out I used roughly 5days finished the task! That’s an overkill for me. With the checker App you have seen in the above link. I was sure I did it >90% accuracy in 5 days.
The last technique I had applied on memorising pi is find a circle objects in the locus of each PAO group (6-digits). And if you ask me to do it again, I think I will add a verifiable code in each locus. Checksum algorithm for large scale number memorization
Probably, it can holds the digits more firmly and it has a certain amount recover ability. 