With all the expensive problems I have had since I bought my Vehicross a month ago I can honistly say that the LPG system hasn't been one of them.
I notice NO drop in power when it switches to LPG infact the only downside I have found with it is that it is more stuff that would need to be removed if YOU NEED TO TAKE THE HEAD OFF because you have NO compression on 1 cylinder.
Anyhow.. I have an 80 litre tank mounted where the origanal petrol tank was and a custom made 25 litre petrol tank beside it. Works well because I still have a boot