I've absolutely loved seeing these 1970 issues of Twen, thank you so much for them. I thought that somewhere in an issue from that year there was a photo feature by Karl Ferris called 'Psychedelic Girls'. Have I missed it?
Thanks for the comment about 'twen' (only six more issues before the magazine folded with the June 1971 issue). Unfortunately, I've no idea if 'twen' had a Ferris feature but you might find the web page below of intertest:https://www.psychedelicbabymag.com/2022/02/karl-ferris-interview.html
Unfortunately I don't have the time to go through past issues of 'twen.' I've uploaded the contents page to most issues where the photographer and illustrator are indicated. I see on US Amazon there is a rather expensive Ferris book by Blurb (the self-publishing outfit):https://www.amazon.com/Karl-Ferris-Psychedelic-Experience/dp/1006737685/ref=sr_1_1?crid=3UHBHPJWZ3DEQ&keywords=karl+ferris&qid=1678015455&s=books&sprefix=karl+ferris%2Cstripbooks-intl-ship%2C141&sr=1-1&ufe=app_do%3Aamzn1.fos.c3015c4a-46bb-44b9-81a4-dc28e6d374b3