How to prevent Meringue from turning chewy/gummy-like?

My attempts at Meringue-making are driving me a tiny but crazy...

No matter what I do, at first, they are still wet on the inside, and if I leave them standing longer to dry out, they get a chewy/gummy-like consistency when bitten into (this is really the best way I can explain it).

I am currently working with 50-60 grams of granulated sugar per eggwhite (depending on what size of egg I have), a slightly heaped teaspoon (not the measuring-kind, just a regular, european teaspoon) of cornstarch per eggwhite. I add a pinch of salt to my eggwhites before whipping them up, then slowly add the sugar. Temperature-variation of the eggwhites did not seem to do much about the chewiness-Problem. I have tried drying between 70 and 100 decrees Celsius (most recipes seem to call for 80).

How do I get them to dry all the way through without burning them? I SUSPECT the fact that I seem unable to get them all dried out is the actual problem!