For short positions, the maintenance requirement on stock greater than $5, is $5 per share or 30% of the stock value, whichever is greater. For short positions in stock where the last sale price/share is less than $5, then the maintenance margin requirement is $2.50 per share or 100% of the stock value, whichever is greater.
As always - call your broker and ask if you can borrow a million shares to short.
Who in the world would tie up $2.5 million to control $4000 in HJOE stock?