We're just enjoying one of these now, and have to disagree somewhat with the previous comments, we think it's an appealing combination. We're using Marie Brizard lychee liqueur, and it stands up to the grapefruit very well but we did use supermarket pink grapefruit juice. My gin choice was poor, we used Edinburgh cannonball which is too strong and lingers on the palate after the fruit has gone. However, as long as you think of it as a sort-of lychee gin martini, I think it's worth trying.....
Totally agreed with Miriam's opinion.. i also tried with 1 and 2 spoons of grapefruit syrup.. but it worse. the balance of the bitterness is hard to adjust.
Unfortunately, the gin and pink grapefruit juice make a very bitter combination - too much for my taste. Lychee liquor is very subtle and cannot balance the bitterness out.