24 lines is normal for the emulation. The old version probably reported back WYSE160 as the terminal type when in 25 line mode but the new version reports back WYSE160-25 which is actually correct. The application is responsible for turning on the 25 line when it needs one. The emulation properly responds to this code.
That said, you can easily make your own wyse160-25 terminfo entry.
As root on the unix machine (assume it's sysv compatible)
First change into your terminfo directory (location varies on different versions of unix), i.e.
cd /usr/share/lib/terminfo
or
cd /usr/lib/terminfo
or
cd /usr/share/terminfo
then
infocmp wyse160 >foo
then use your favorite editor like vi to edit foo
A typical first uncommented line looks like this:
wy160|wyse160|Wyse 160,
change it to
wy160-25|wyse160-25|Wyse 160,
Then go down to the entry containing the number of rows. i.e:
cols#80, lh#1, lines#24, lw#8, nlab#8, wsl#80,
change it to
cols#80, lh#1, lines#25, lw#8, nlab#8, wsl#80,
save your foo and and do:
tic foo
You should now have a wyse160-25 definition in your terminfo database (under w)
If you application uses termcap instead (unlikely) just edit /etc/termcap and copy the wyse160 lines and make similar changes to the new copy.