Welsh ponies are TOTALLY suitable for adults! I have a few of my own. I think it’s silly that some people insist that adults ride horses rather than ponies - ride whatever you want to ride, and have fun!!
As a child I rode ponies, then as a teen was pushed into ‘needing’ to own a horse, so I did… went though 4-5 horses until present-day me finally decided that ponies are AWESOME and why did I EVER decide to give them up!? I love them so much I decided to start breeding Section B Welsh Ponies, and haven’t looked back! Go with your gut, and start having fun on that pony.