You'd still want to define a virtual server on the same subnet as the server(s). Enable SNAT automap on the virtual server to ensure that replies from the server(s) come back through LTM. Then make sure clients are connecting to the virtual server IP--not the server IP.
You can use tcpdump to check the packets:
tcpdump -enni 0.0 -Xs0 host CLIENT_IP or host SERVER_IP
-e = print the layer 2 information
-nn = don't resolve ports or IP addresses to names
-i 0 = all switch port interfaces
-X = print hex output for packets
-s0 = don't limit the packet size that is recorded
Aaron