Nope, I'd never heard of him either! However, it appears that he may very well be the first person to propose movable aerodynamic devices controlled by the driver:
Would it not be practicable to fit light racing cars for track use with a couple of ailerons one projecting each side of the car about the back of the driver's seat and at the level of the chassis frame .... the adjustment could be partly by hand and interconnected with a pointer and scale in view of the driver so that settings found suitable .... could quickly be made with certainty. Has any reader [of Autocar] tried devices on the lines indicated?
That's a quote from a letter published in 1924.
Ironically, my source for it is William Court's "Power and Glory" - writing in 1966, Court says with authority "to this day no racing car has been fitted with ailerons", conveniently ignoring the May brothers' Porsche from the 50s. Oh well, even the greatest writers get it wrong sometimes! Even as he wrote, the McLaren team were making their first experiments with what became known as wings ....
Hellstrand was probably influenced by the Opel Rakete, which had fixed wings between the wheels, but his idea for movable aerodynamic devices would have been a quantum leap in the 1920s. Just imagine ......