This paper analyzes the variation found in Majorcan Catalan regarding the realizations of /i/ and /u/ in contact with other vowels, which depend on the nature of the vocoids themselves, the syllabic position in which they occur, their surrounding segmental context, and the geographic origin of the speakers. Leaving aside faithful hiatic solutions, their realizations range from different degrees of strengthening to fusion and deletion, and further coexist with some instances of /v/-weakening. To account for these patterns, we provide a unified analysis within the split margin approach to syllable organization (Baertsch 1998, 2002), with phonetic grounding supporting the distinction between [+high] and [-high] for palatal glides (but not for their labial counterparts) and the approximant character of /v/ in intervocalic position. We also show that, in order to explain the whole variation, markedness constraints referring to the harmony of segments in intervocalic position (Kirchner 1998; Uffmann 2007), and their specific interaction with faithfulness constraints, are needed.