Even with the CNG cylinder installed the Original board and aftermarket as well fits fine !
I wonder what was the issue before removing the cylinder tho
For the speakers i would prefer you to buy a similar fibre board and install the speakers in it because i have installed the wooden board for speakers and i have to access the boot area by folding the seats which becomes irritating at times
With original fitting you will be able to access the boot easily , a copy of original board is easily available for 3k