DSF

I have a poly t shirt, can i sublimate both sides?

Yes you can

You can but be careful after pressing the first side for a second transfer.

What I mean is that if you will just turn the t-shirt over after pressing the first side you should be aware that the first side will still get hot and some ink may transfer onto the base of the press. If you're going to do it this way place some baking paper down first just in case - and also note that if there's any movement whilst the garment is hot you could have some shadowing (i.e the position of the transfer changes slightly and it continues to sublimate).

I'm quite lucky as my base plate is big enough to feed the t-shirt onto the plate so I'm only ever in contact with one side at a time.

Put some paper inside the shirt to stop ink transferring through the shirt.

If you have a press which heats both platens, you can do in one pressing (back and front at same time), or may get away with it on a normal press, but the bottom side of the shirt won't get as hot, so you may need to adjust your time/temp to compensate for this.

ty all, its only a childs t shirt and my press is too big to feed the t shirt on to do each side seperatly, thinking about it i might do words on back in vinyl, then sub the front design.

As has been said above as long you put something under your t shirt so the first side does not transfer onto the bottom of your press while you d the 2nd side and place some paper inside the shirt it should be fine