Send delay?

Please can you help a hardware engineer, who almost understands what he's doing.

I'm using sTunnel 4.21 on a Windows 2000 machine, to provide a TCP program with SSL. This works very well.

However the application is very time critical and must finish sending block of XML as quickly as possible. I suspect there is a delay in either sTunnel or openSSL, while it waits to see if there are any more characters before sending a packet. Is this correct?
If it is, is there a work round.