If you try to back flip the Savage, the roll bar does nothing to protect the engine head if you don't land on all four. Heck, I've bent the crap out of a couple of engine heads...even with this inexpensive mod...like I said it offers a little protection.
Either go with a full cage for best protection or look into some head mounted skid plates. I know there are a few companies out their that make cooling heads that come with them. I seem to recall that the new TRAXXAS 2.5 (pardon me whilst I wash the bad taste from my mouth) comes with one.
Until you get the full cage, become an expert at keeping the truck on all four most of the time, zip ties are cheap and pretty effective for glancing blows to the head of your engine. Full on landings...well you take your chances there.