(Westport Innovations story updated for latest Nasdaq short interest data)NEW YORK ( TheStreet) -- I want to say it's time to buy Westport Innovations ( WPRT), but that might be reckless advice given the seemingly limitless free fall in shares of the natural gas engine maker. What I will say is that it's at least time to put this stock back on your watch list, but don't expect more than to watch it fall even more than it has already. I think it's all that can be said right now of Westport Innovations, as shares slipped below the $30 mark on Tuesday, for the first time since last December, a long ride down from above $50 mark the shares hit on March 21, and its 200-day moving average now a distant memory. I'm not going to name the Wall Street analyst whom I emailed with Tuesday -- he might get in a little bit of trouble for expressing some honesty on the name that doesn't reflect the simple world of buy, sell and hold ratings -- but here was our exchange: Me: "Does it concern you that it's maybe headed down, down, down and the shorts are going to own this stock for a while, or does it seem like an obvious buy here because there is too much support for it not to rebound? Even if the shorts are in it for a future year payday when Cummins ( CMI) says bye-bye for good to WPRT relationship, I don't see why it would necessarily trade straight down between now and then. I could see this as a $12 stock in 2015 but a $35 stock next week."