Put in a couple large 30 gallon royals several years back. They are healthy, thriving and probably doubled in size. Around 20-25 feet tall, ginormous base around 7 feet diameter at ground level. But there's a 4-6 inch gap at the bottom where the woody base ends and a bunch of roots are growing. I know this is a relatively normal feature with some palms, but I have the urge to pile up several wheel barrels of dirt around these. Wondering from the pros here, what is the best course of action? Mound some dirt up or leave it be? TIA, DT...