There's not much that I've been able to find on 7 Poets Press and Carl Larsen's other publishing, but here's what I've been able to piece together:
His first little magazine titled Existaria was published in Southern California (Hermosa Beach), ran for 7 issues in the mid to late 50s, and was a model for E.V. Griffith's own little magazine Hearse. His second periodical was rongWrong, and was published quarterly for 5 issues in New York in the early 60s and was co-edited by James Singer under the 7 Poets Press imprint. At this time, 7 Poets Press also started issuing chapbooks -- I think there were seven or eight in all. Also, in the early 60s was the periodical Brand X, which seems to have been modeled after Floating Bear, and ran for 12 issues each month in 1962...