I hav seen many FF CNG cars with woofer installed and dnt think will have any effect on the cylinder. Now thre r 2 ways of installing a sub in a hatch, either on the board or make an L/ported box and keep it on ur back seat. L box will surely hav better bass as compared to ported one but will occupy most of ur back seat. The one on the board will do the job too but less space below the sub will effect the bass. No need for under seat subs as they hardly give any bass and to my own experience while using it in santro, not worth the money.
