I have a 480V Delta to 240 Y transformer?

I want to run backward in order to boost 208/60/3 to 480/60/3. I neither want nor need 277 on the secondary. I will bring in 208 to the primary side (now wye) along with the incoming ground. There will be no neutral. The ground will go to a 3-way lug on chis ground on the transformer, then on to building steel and from the same lug on transformer chis to the secondary 480v panel ground. I will float the X0 on the primary. There is no under size bonding jumper from x0 to chis to remove and it looks like x0 is completely floating. 225amp OCPD (breaker) feeding 3/0 on primary and and 125 amp breaker on secondary. The transformer is 150kva which is a little big but I think that is ok it is just bigger than needed. On trial the 225a breaker easily handles inrush. There is a small, mystery tap next to x0 and right now the electrician has incoming ground going to that lug. I don't like that idea. Any thoughts? Thank You.