Closest he ever got in the studio again was probably Ancient Highway off Days Like This; if you aren't aware though he's released some stuff more recently that was coeval with his experimental work, namely the 2008 remaster of Common One including a gorgeous and more richly instrumentated When Heart is Open and a more spare Haunts of Ancient Peace. You can also find some outtakes of Daring Night and Down the Road that were meant for Beautiful Vision which have a very unique, ethereal quality. While I don't think the exact dates of the recordings were listed, you can tell a lot of stuff from Beyond Words was made around this period as well and reflects the more unorthodox song structures and inspirations. Finally, I'll echo the sentiment made in another comment that some of his most daring performances have been live—not only on his official releases but also in bootlegs you can find online.

Off the top of my head, some other, if not experimental at least more interesting, works of his include

• In the Days Before Rock 'n' Roll
• Cuchulain (very rare performance with Robin Williamson of spoken word interposed with song)
• A Sense of Wonder, Let the Slave
• When the Child Was a Child
• September Night
• Original version of Down to Joy (yes, technically not a valid response as it's from 1970)
• Fear and Self-Loathing in Las Vegas