A roll bar loop with just two mounting points is no use at all. The bar will just fold over with any serious impact and may even be a danger to you.
Three points is a bare minimum in theory but four points is considered the best minimum in practice for both safety and chassis strengthening.
Notice that even though this one is just bolted in there are plates under the floor to stop the bolts simply pulling up through the floor.
If you have chassis connectors it may be possible to go through the floor and weld to those as long as you also weld to the floor. However the chassis connectors may not be far enough apart to just go straight down onto them.
Here is a slightly stronger version of the same thing.
You might want to make something with elements from both these designs.