Hi Les
whatever stops the cells rattling around is good....
as far as cell themcells....I generally use
https://www.ebay.co.uk/itm/10er-Akku...72.m2749.l2649
I re-touch all the welds as they rubbish. but the cells have been good so far only one actual cell failure in six packs.
I have rebuilt 10+ nimh batteries and 6 or so saphion.
Hope this helps...