Most efficient way to build a big variable length string?

[bplus]

for @ahenry3068

That's another problem, UDTs (User Defined Types) originally started way back in old GW Basic could always do fixed length strings when it came to saving or retrieving to/from files but variable length strings are new to QB64pe (not QB64? I think...) anyway varaible length strings still can not be used directly to file data.