Fresh from two years playing Peter Allen in The Boy from Oz, Todd McKenney is back on the boards.  This time he's going it alone, entering the world of cabaret, where a nightly audience of just 120 can get up close and personal.     The Allen persona looms large in this production -- which McKenney hopes to tour nationally -- and why not?  The tap dancer from Perth made Australian musical history with Allen and it's this relationship his fans will come to celebrate.  Even so, a good number of the audience admit when asked that they haven't seen the musical.  But, by the time Allen's music takes over the show, they are churned up and jiving to McKenney's superbly vital performances.     The problem with this show is with much of the other music that McKenney sings.     With just a microphone and no maracas or glittering shirts, McKenney the singer misses the emotional mark in songs such as If I Only Had a Brain and the classic Mister Cellophane, where the equivalent of high-powered energy needs to come from the soul, not the body.  A few tweaks might improve things.     McKenney's entrance after a short keyboard introduction from the extremely talented Tim Minchin needs a big song to get things on the road.     Instead, we get the star looking like he's buried in a folder of memories and trying to avoid a confrontation with mafia boss Tony Soprano.  Come on, Todd.  Didn't Allen teach you the value of a good entrance?     A superb reworking of Stephen Sondheim's I'm Still Here, tracing McKenney's career, would have been better as an opener instead of near the show's end.  There's nothing like logic and order to smooth out the rough bits.     Stage space is limited but the energy level in this personable performer still finds room for tap dancing, in more ways than one, and there are trademark twirls thrown in for good measure.     The rapport between singer and pianist should grow, but as yet the repartee is often too in-house or mumbled, so the audience can't join in the fun.     The performance lifts after the interval, with McKenney totally involved in the lyrics of classic Allen hits such as I Honestly Love You, Fly Away, Taught by Experts and Tenterfield Saddler.  Suddenly the body language is more confident and the delivery driven from the heart.  Home ground at last.