Rather than a straw, have you tried flower pics? And when I tape my flowers together, I try to ‘graduate’ the thickness of the stem by trimming with pliers as I go down the stem…. oh that sounds poop, really hard to explain!!!!
I start taping together with one stem then once I’ve added another stem, I trim the wire of the first one and so on….
This prob hasn’t helped at all – sorry!
Beautiful cake by the way xx