We had a discussion about this last year and the upgrades,you might try the search menu to find the information,I seem to remember a lower hull upgrade that was pretty costly. Sax
I have the Tiger 1 special edition and it is great.
Apart from your first post about a 'used HL' if you're able to pick up used a special edition it has loads of hop ups on it already,like the better hull,metal wheels and tracks,metal gearboxes etc.