Thanks for your thoughts about the matter, poppy! We're really doing rather good with the sidepull, however, I have noticed that he's had a bigger tendency to keep his neck higher and stiffer if the reins go from his cheeks, compared to when the pressure points on his nose are lower and work more on his poll. When we tried the hackamore on him it seemed more that its' cues are clearer for him. I guess I might go with using both the hack and the sidepull for a while, working on his responsiveness in the sidepull and helping him getting accustomed with the movements in a hack, and I will place the reins higher on the hack, so that the leverage is very light.
Did a great recording session at the studio with my band tonight. We're working on a cover for a song of a Lithuanian neo-folk band whose work we appreciate very much. They're informed and ok with us making a cover for their song and we hope it means further cooperation. :)