You can specify the page size to use when creating a Btrieve file by setting an attribute in the Xfh2btr configuration file as follows:
BTRPAGE:nnn
where nnn is a byte value in the range 512 to 4096 inclusive, in multiples of 512 bytes.
If you do not set BTRPAGE, or you specify a wrong value, the page size defaults to 1024 bytes.