Try this
Via XDA...
"Expand SMS Typing Area
Use the freeware
Total Commander and edit the file 'thread_sms.htm' in the windows directory.
Look for this part: <inbox:content id="COMPOSESUBJECT" width="98%" height=35 spell...
By changing the 'height' (in this case 35) to 50 or 70 you will get 3 or 4 lines for text replies, respectively.
Soft reset after editing the file.
(Credit to koppee1)"