True, there does not appear to be much backward slant, however there is a lot of information on Dogpile or Google, etc, and it states that in forward flight all power went to the forward facing props, none to the rotors. It did however have small wings so some of the load was taken by them. For model purposes it would be necessary to build in the rearward slant of the rotor shaft to give the rotors a positive angle of attack.