In his review James Clackson points out correctly that it is misleading to say, as I do on pg. 342, that the monosyllabic scansion of dat. sg. ei is typical for Classical Latin. All forms of is, ea, id were less common in Classical (Augustan) poetry than prose and the oblique forms were especially rare. See Meader 1901 for some statistics. The dative singular is not used at all by Vergil or the Elegaic poets. There are, however, a number of instances of ei in Late Republican and Imperial poetry:
At Catull. 82.3 (eripere ei noli, multo quod carius illi) ei must be a monosyllable, but at Ps.-Ov. Hal. 34 (semper ei similis quem contegit, atque ubi praedam) it must be an iamb. Similarly at Germanicus' Arat. 333 (talis ei custos aderit canis ore timendo) and 457 (lactis ei color, et mediis via lucet in umbris). The form ei also occurs in epigraphic poetry once as a long monosyllable at CIL 3.10501 (= Buecheler CLE 489, Aquincum): vox ei grata fuit, pulsabat pollice cordas and once as an iamb at CIL 3.754 (Buecheler CLE 492:15, 3rd cent. CE, Nicopolis): intima nulla ei quae non mihi nota fuere, a poem which Buecheler says is omni genere vitiorum deformatum. There are some other instances of ei in CLE but the scansions are uncertain. Since the form was so rare it hardly makes sense to say that any scansion was typical.