@Ray--Opo I got Vlad's Kane mat when he was around 5 lbs I think. I don't see why you'd have any issues as long as the you've got it controlled by a thermostat. Also - do you have an infrared temp gun to do spot temperature checks? That way you can keep an eye on the surface temp of the mat and make sure everything is safe.
I went with the 18" x 27" (sometimes listed as 18x28) model which is still plenty of room for Vladimir at 23 lbs. I'd recommend to go with that size if you have the space, as Opo will have plenty of room to grow into it. But even the little 18" x 18" would be good for Opo if you don't have room for a bigger one.
We got ours from Tyler at Tortoise Supply: https://www.tortoisesupply.com/kane
I went with the 18" x 27" (sometimes listed as 18x28) model which is still plenty of room for Vladimir at 23 lbs. I'd recommend to go with that size if you have the space, as Opo will have plenty of room to grow into it. But even the little 18" x 18" would be good for Opo if you don't have room for a bigger one.
We got ours from Tyler at Tortoise Supply: https://www.tortoisesupply.com/kane