An adjective appearing as nórima within the sentence nése nórima rokko “he was a horse strong/swift at running” in notes from the late 1960s (VT49/29). In Late Notes on Verb Structure (LVS) from 1969 it was nŏrima “running, swiftly a course” with a short ŏ (PE22/156). In these notes Tolkien indicated that the suffix -ima only had stems with a long vowel for adjectives of possibility (from transitive verbs), and when used with intransitive verbs the stem had a short vowel, and had “the sense possessing to a high degree (at all times & by nature) the property mention[ed]”. As such, I think norima is the best form for this adjective.