I know Laird strongly recommends to use Hardware Flowcontrol, but my design does not support at all. Besides interconnecting the RTS and CTS together, what else do I need to do? I understand the risk of packet drop, or buffer overflow.

Laird PC software such as firmware upgrade tool for Classic Bluetooth modules, and BCSP mode enable program require Hardware Flowcontrol as well. This means you will need to interconnect the PC RTS and CTS as well.