Generally 10-20MS is fast for a relay.
Keep in mind for 80M, 5 relays have to switch so you always plan for the slowest
which in the case of this is a cascade of two.
To go to transmit The Raduino activates K1, TX+ is its output and that activates the remaining?
3 band pas filter relays as needed and K3 always.
So RX to TX switching is the sum of K1 and K3 switching time.? 20mS would be optimistic.
Allison