if your peer id is the first thing sent you might want to use req.payload(0,25).
your config works for me if I client sends at least 26 bytes within inspect-delay period.
note that you can write tcp-request content accept if WAIT_END || { req.payload(0,25) -m found } (or req.payload(1,25) if it’s what your need) so you don’t have to wait 2s every time you connect.