@leigh It would be helpful if you posted a link to your table. Others can chime in, but tables have notoriously had problems on small devices. (All tables, not Joe’s stack in particular.) I think Joe’s stack does horizontal scrolling when on a small phone device, but not 100% positive. At any rate I don’t think horizontal scrolling comes naturally to most users so you’d have to let them know about this feature, or simply suggest they use a tablet/computer to see the full beauty of the table!
Using column widths in percentages should help a lot (instead of pixel widths) as then the table will adjust to those percentages based on the “available space” which will be different on computer, tablet, phone. This will help, but in some cases will still lead to less than optimal viewing.
You also might want to look into Bryn Owen’s Flex Table stack:
Bryn has some features that may be more important to you. I have both Joe’s PowerGrid and Bryn’s FlexTable and I’m glad I have both: depending on the situation I may use one or the other.