I did not open the latest links, but you seem to be suggesting that the original design is questionable.
I actually designed a studio flanger back in the 70s (Loft), and did a kit BBD delay/flanger in 1976 for popular electronics.
Not rocket science but I don't feel like tweaking some one else's design. I generally discourage that because in most cases you can't make it better... this seems like a possible exception.
I will point you in the right direct, especially about you complaint of too much bass. Like i said before that circuit uses HF pre/de-emphasis, so HF are boosted in the first circuit block, then cut again in the later circuit block. The net effect of that is to reduce HF noise from the BBD path. So I repeat, if you perceive too much bass, check that the pre-emphasis circuit is boosting the highs properly. HF de-emphasis without the complementary pre-emphasis could sound bassy.
JR