I have never had that problem, but I have always read that one must be sure to spread the meringue all the way onto the crust. This allows the meringue to be anchored to the edge. Any shrinkage will be turned into stretching rather than a smaller diameter. I would suggest that you drag the meringue all the way over the top of the formed crust edge to create a mechanical bond just to be safe. I don't know anything about gluten free crusts and the mechanical bond might actually be required. For regular crusts, I think the meringue just sticks to the inside edge as long as it touches it well all around.

edit: Also, I just l recently learned that one must not over bake the meringue (only brown the peaks) or it will stick to the cutting knife and be crushed rather than cut thru.

Thanks. No, haven't made a meringue pie since we took gluten out of the house. I probably was stingy or kept the crust showing to make it "pretty" before cooking.
Another question. I plan on making it tomorrow for it to set until Thursday. Should I do the meringue on Thursday or tomorrow? And should I keep it in the fridge or on the counter overnight?

I had skipped the humidity issue because humidity is low in winter and I didn't think about the cooking with steam problems. I have always made a presentation pie on the day of the event. I suppose I shouldn't be considered one to give the best advice since I recently had my own question about thickened filling on this forum; but with a return to following directions without distraction or rushing, my problem was resolved. I suspect that for best thickening, you should stir constantly and at most only cook one more minute after you feel the thickening begin. I believe that the filling has begun to relax with over cooking which has led to more over cooking. It has still gelled up for me in three hours. I bring this up because it seems a lot easier to bake it all together in the same hot oven if you have a few hours before presentation.

I leave my left overs on the counter. Humidity makes the meringue stiff. It is another reason to serve on baking day. Actually, I keep the pie on top of the refer. I have a counter surfing hound who knows that leftover (or not) pie is better than dog food.

I really hate meringue that has been refrigerated. It might be fine if allowed to come back up to room temp, and it might be fine in a beverage cooler or something (50 degrees, rather than under 40). Meringue should taste like angel's wings, and when it's refrigerated it's more like undercooked omelette. Lemon curd is good cold, but also tastes better when it's not chilled. That's all subjective, though.

In general, I think all pie is best kept in a good, ventilated pie safe at room temperature, and eat the danged pie before it gets moldy!

That's funny about the humidity thing because I spent part of the day to get the humidity way up in the house. Good thing it didn't work! I think I will make the pie on her birthday first thing and let it set through the day. I am so excited to make it. I rarely, if ever, bake full on sweets anymore. Unfortunately, I can't have any :(. I will do something else with the extra pastry for me. Hmmm, better start thinking. Thanks.