Impressive amount of research! I see a Jamaican rum version in the comments, which is worth noting. J.A. Groshusko's 1933 Jack's Manual uses Jamaican rum.

I followed Ander's recipe and used 22.5ml brandy, 22.5ml Havana Club 3, 30ml dry curacao, and 15ml lemon juice. Then add 10ml of demerara syrup and it tasted much bater.

Very good - I used 45ml of cognac, 15 ml of Curacao (instead of Cointreau), 15ml of white rum and 15 ml of lemon juice.

I followed the recipe and it was good, albeit a bit mild. The second time I made it I used gold rum and it was much more to my liking, a bit more boozy.

Made it exactly like this and it absolutely works. It is really all about what you use. The Cognac comes through first. The rum choice is even more important, where if you use a charcoal filtered rum, that's probably where there is this 'cancelling' occurring. I used Havana Club 3, and I get the rum. The slight sherbet-y sweetness comes from the Triple Sec combined with the tiny sourness of the lemon. It works very well.

Best Spec I found…
1oz Cognac Pierre Ferrand
1oz Rum Appleton 8 yr
3/4 Lemon Juice
3/4 Dry Curaçao
tsp (5 ml) Demerara Gum Syrup

hated it, added 15ml lemon and 10 ml simple syrup and loved whatever came out.

I feel like the Cognac and rum really cancel themselves out so I am only left with a sweat hard lemonade, which is something I could achieve with just vodka and lemonade. Maybe I am just not a fan of split base drinks but I feel like a cocktail should be showing off just one spirit.

Sadly this cocktail didn't taste like anything for me (and I didn't have covid lol) everything sort of cancels each other out. If you like mild cocktails you might like this one.

Very nice. Like a more delicate version of a daiquiri.

Very nice after dinner cocktial. I find these proportions to be perfect. Will make this again. As a bit of history my Mom always spoke of this cocktail.

Not bad. No dominant flavours everything is balanced. Enjoyable

A little too sweet for me. My wife liked it, but I prefer to cut the triple sec with something sharp like tequila. I’d rather have a rum drink over ice to dilute it a bit more as I’m drinking so this cocktail probably wasn’t right for me from the get-go.

Very easy to drink. Good balance. I agree with the addition of the sugar syrup.