Do two things
1) Check the application logs on SLT side to see if there were errors generating the conversion objects. I tried your code on another table and got what looks like a syntax error here.
2) Try using the following code instead
CONCATENATE <wa_s_lfa1>-name1 ' ' <wa_s_lfa1>-name2 INTO <wa_r_lfa1>-zfullname SEPERATED BY SPACE.
Sometimes syntax is everything 
Regards,
Justin