Is it possible to boot already not signed IPSW without saved shsh in iPhone (SE) with pongoOS?

[likemusic]

I need in result to backup files from iPhone SE in recovery loop boot (seems because there is not enough free storage space to upgrade to new signed ipsw - error 14 when 75% of file system sent).

Therefore I want to restore 13.x version (because it has weight less about 1 GB).

Or may be is there a way to decrease size of current signed IPSW (iOS 14.3 (18C66) - https://ipsw.me/download/iPhone8,4/18C66) and boot it, to have access to iPhone file system?

[likemusic]

#10 - related issue with some useful comments.

[likemusic]

Perhaps (according to comment) there will be a module that provides access to the file system.

[likemusic]

#9 - seems related