Citric acid limits? + a few elderflower wine questions

So its the season for it, and like many others I'm getting on the elderflower bandwagon. I'm gunna try to make 5gals, and have currently made the base solution for it.

I didn't use a recipe, just general formula for elderflower cordial thats worked in the past with a few tweaks.

So far:

70-80 elderflower heads with stems removed
2 small lemons, a lime, and an orange (juice and zest of all)
a good squirt of lemon juice
handful of mixed currants/raisins/sultanas for a bit of body

into about 2250ml very hot water with 7lb sugar dissolved

done 48 hours ago, currently left sat unstrained, will strain tomorrow as trying to let wild yeasts start of a little (is this a good time frame?)

then the loose plan is to strain through muslin into the 5gal container, top up with more sugar and water to appropriate levels for 5gals of wine, add a bit of commerical yeast.

now my question is that with all the citrus in there already (juice and zest) if I add more citric acid, at what point will it interfere with fermentation? normally I would add 140g to this if it was cordial. Should I wait till fermented to add, or do it now?

Also, any general opinions on my process would be appreciated. I have a feeling I may need to go foraging for some more flower heads if it doesnt taste strong enough when topped up. If so, will repeat the process (with less dissolved sugar) to add a few pints of flavour to it.

I'm really liking the idea of making a flavour infused sugar syrup/cordial solution and then topping up with water and sugar for brews. opinions?

and as always, thanks

As for wild yeasts... you are leaving yourself open for infections from bacteria. I would sulfite and throw in a domestic yeast.

As for the acid... the general rule of thumb is a pH between 3.2 and 3.8. Higher than 3.8 will get infected and taste funny. Lower than 3.2 will just taste bad. So if you add more citric acid, you want to make sure you don't fall below 3.2. Wine makers tend to add it at the beginning, where as mead makers add it continuously as the pH in mead isn't constant.

If you want a cordial, then make a cordial, but if you want a strong wine with elderflower flavor, you will either have to back sweeten, or fortify it, or both. The more alcohol with the wine, the less flavor you are going to get.