Not sure if that's a good riser wood, but you should seal the ends of your pieces to help control checking and splitting of your pieces..you will have to get moisture content down to 8%?? or so .. maybe someone with more experience will post ..I used titebond wood glue to seal the ends of a piece of hickory a few years ago. You might have to add a few pieces of glass or an I beam to make a strong riser. I have heard that mahogany can be brittle. I did a search and found that the mahogany you have is likely West Indian mahogany or Cuban Mahogany, didn't find alot of info on it other than it was used in the cabinet and furniture industry