Pool table on deck

Hi there.I have a problem and I hope this forum can give me some help and push me in the right direction.The forum was very helpful for me in the past but I could not find the answer for my new problem.I have a roofed deck mounted to my house on the top level.It is 10m wide and sticks 4.6m of the house and I made a room out of it.Now I would like to put a pool table up there that is about 500kg. The pool table have six legs and only the middle set of legs is sitting on a joist. The outer two sets of legs sitting in between two joist.The deck is build with 250mmx50mm f17 hardwood joist and they are ~450mm apart.On top of the joist is mixed hardwood decking (85mmx19mm) and on top of the mixed hardwood is yellow tong flooring installed.On top of the yellow tong, I want to lay hybrid flooring. The pool table will sit on six hardwood flooring pieces, so it is not destroying the hybrid flooring.I have a bit of bounce in the floor and I think it will be much worse with the pool table.My question is how do I make the floor more strong?I was thinking to install two more joist direct under the outer sets of pool table legs and screw 180mmx6mm flat bar on one side of each three joist that carry the table.The price for F17 is $50 a meter and for f27 it is $110 a meter what is a lot of money.Is there a better way to do the job? And if not, should I use the f27 or is the f17 also ok?Or should I just use steel. Like a c section or t section? And what size should I use?Thank you very much for any input.Chris

All line breaks somehow disappeared. Here again for easier reading.

Hi there.
I have a problem and I hope this forum can give me some help and push me in the right direction.
The forum was very helpful for me in the past but I could not find the answer for my new problem.

I have a roofed deck mounted to my house on the top level.
It is 10m wide and sticks 4.6m of the house and I made a room out of it.
Now I would like to put a pool table up there that is about 500kg (9ft slate table).
The pool table have six legs and only the middle set of legs is sitting on a joist.
The outer two sets of legs sitting in between two joist.
The deck is build with 250mmx50mm f17 hardwood joist and they are ~450mm apart.
On top of the joist is mixed hardwood decking (85mmx19mm) and on top of the mixed hardwood is yellow tong flooring installed.
On top of the yellow tong, I want to lay hybrid flooring. The pool table will sit on six hardwood flooring pieces, so it is not destroying the hybrid flooring.
I have a bit of bounce in the floor and I think it will be much worse with the pool table.

My question is how do I make the floor stronger?
I was thinking to install two more joist direct under the outer sets of pool table legs and screw 180mmx6mm flat bar on one side of each three joist that carry the table.
The price for F17 is $50 a meter and for f27 it is $110 a meter what is a lot of money.
Is there a better way to do the job? And if not, should I use the f27 or is the f17 also ok?
Or should I just use steel. Like a C-section or T-section? And what size should I use?

Thank you very much for any input.

Chris