Hi @ZeusEx,
Yes, you have to burn the Sik-radio boot loader (and the hm-trp-sik-radio-fw) first.
I got some plain vanilla HM-TRP’s with a different (HopeRF) firmware too.
After updating the radio chip to Sik-firmware they where fully compatible with other existing (2nd gen) 3DR-radio’s.
To be able to burn a sik radio boot loader to the chip you need a Silabs prog adapter:
DEBUGADPTR1-USB
The necessary wiring can be found here.