Try scaling the gin up to 2oz, or using one that’s higher proof like Tanq or Broker’s.
Do you have a recommended martinez spec by chance? Baring that have you used anything besides london dry gin and what would you say Plymouth works best with if so?
The Pegu is a fine established recipe, upping the gin content of proof isn't really an issue and personally I find those gins to be flat, the 2 London dry's I consistently keep in my cabinet are Boodles and Citadelle as I find them to be deliciously herbalicious. That sounds pretentious as all hell...
As far as a Martinez... that's not a cocktail I'll make at home by the fact I'm not going to buy a one-off liqueur like Maraschino so I'd say go with the IBA spec for it but make certain you use a quality vermouth and orange bitters.
As for Plymouth gin, I do keep a bottle of the regular strength Plymouth and as for cocktails with it I like the 50/50 Martini with Lillet blanc in lieu of vermouth, it's an easy sipper with lots of flavor.
There's the very simple Gin & IT, which is still a 50/50 Martini but with sweet red vermouth. I'm partial to Cinzano, myself.
IMHO both the Tom Collins and Gimlet work better with Plymouth than with London dry, and of course an Old Tom gin Gimlet is so good that's it's dangerous.
Plymouth also works well in a cocktail so old it's an antique, the Classic Gin Cocktail, 2 oz. gin, 1/3 oz. curacao, barspoon of syrup & 2 dashes of Peychaud's bitters.
Don't try to order it at a bar, 99% chance the bartender won't know it and you'll be served a G&T.
cheers!
I wrote this while sipping an El Presidente.
1.5 oz. Bacardi white rum, .75oz dry vermouth, .25 oz Ferrand curacao, 1 barspoon grenadine.