OT: Stupid questions for the pros, vol.1

[Vincent Volta]

Hi all,
Im into building amps right now, and was building the power supply for a 50w one. The plan was to use a salvaged transformer from a dead amp ( along with the speaker and cab AND front panel) but the transformer was too big for the project I had. I needed 26v on each AC rail and I have 30,5v which leaves none of the security margin indeed.
When I tried it though, I forgot to hook the center tap to gnd., and the voltage decreased instead of going up after the rectifier. The voltage should have been 42v and I had 27v there.
In short, I got two rails positive and negative from the transformer, ignoring the center tap and I got a lower voltage which seemed ok for the amp. The amp wasnt tried with this supply, and the question is if this is a safe procedure or just a spiffy thing that will blow something up. If it is, I have to buy a new transformer or either build a bigger amp... using a new speaker and cab (bummer...). Thanx for your patience!