I would try doing several 10ml batches with different flavoring amounts to start, just taking your best guesses. 60ml of juice is too much to waste making unsatisfactory juice. At least for me, I go through many iterations before I have a mix I'm happy with. Sometimes many, many, many iterations... lol. Just put numbers on the bottles and keep a paper handy for your mixing notes for what you did with each mix for reference later after you taste it.
With straight up fruit flavors like this one you shouldn't have to wait for weeks to taste it. Sure it will change some over that time period, but you should have a fairly good idea of the flavor after a day or two. If you have an RDA, use that for quick tasting to get an idea of how the mix is tasting without having to fill a tank. Try to use fresh cotton for each mix so you don't get flavor mixing from the last taste test mix. And single coil works best for me, and easiest. I use a bowtie wicking method for this. Just a short piece of cotton that protrudes just a small amount on either side of the coil. The cotton does not touch the RDA deck... just protrudes about a quarter inch on either side of the coil. like a bowtie. I drip some juice to saturate the coil and cotton and that is enough for about 2 or 3 puffs. If I'm not sure by then if I like the taste I'll saturate the coil again until I have an idea of the flavor. Once I'm happy with the flavor I'll try it in a fully wicked RDA, tank or squonker. It's really quick to pull the cotton, dryburn the coil, and re-wick the coil this way so you get a fresh start for each tasting. Oh, and try this at lower power settings, I tend to use 30watts with a .5 coil build for tasting.