These days, for simplicity / convenience, I generally use Mrs Balbir Singhs excellent spice blends & recipes - with variations to suit my/missus taste.
I have just checked a content chart I made from her blends to check for Kashmiri chilli content. The following blends contain Kashmiri chilli :-
Biryani
Butter chicken
Tandoori rub
Roast lamb raan
Masala chops
... I have made them all. In not one case have I noticed any hint of bitterness. I can only assume they know of & use the real McCoy of Kashmiri chilli.
The madras I make is a toned down version of her Goan Vindaloo - where you use your own chillis - type & amount according to your taste. This has been great using green Serrano chilli. Trying the dried 'kashmiri' was horrible - so clearly it either wasn't true Kashmiri or as I have read - maybe grown with too little water which gives chillis a bitter taste supposedly. It will be interesting to see what results I get from the 2x Kashmiri chilli plants I have ordered - due april sometime