I have only ever made full-on macaroons, and I expected them to be chewy and not crisp (and I've added not/Sugar or a mix of vegetable gums including Xanthan, to get more body) so I'm at a loss. The pavlova is supposed to have a little gooeyness or chewiness too.
For a plain crisp meringue, I have tried out the Heavenly Desserts brand of Sugar-Free Fat-Free Meringues {www.d-litefulbaking.com} and I guarantee you they are so 'crisp', they crack apart in the mouth. After that they "goo down" a bit, just like sugary meringues.
So here's the ingredient list for those critters (Lemon flavor):
Modified Malt**, egg whites, water, natural lemon flavor, tumeric color, xanthan gum, salt, vinegar, sucralose (Splenda brand).
**there's a waiver about polyols, so the modified malt is a nice way of saying Maltitol. There's 4g polyol per 3 pieces total weight 4.5g.
In short, I'm guessing, based on experience, you *need* a sugar bulking and texturizing replacement for a crisp meringue, not just Splenda. The filler (maltodextrin/dextrose) in the Splenda is not enough.
A meringue, therefore, is technically "sugar" held together in a light (very light) protein matrix provided by egg whites.
Hope this helps.