As those two properties do not need a custom set func, yet need recalc of strips drawing/positions in addition to usual rna_Sequencer_update() (cache invalidating), I renamed rna_Sequence_frame_change_update to do_sequence_frame_change_update, and made a new rna_Sequence_frame_change_update which is directly usable as RNA update func, and call both the strip and cache update funcs. Thanks to Sergey for advices!