Fresh, Gray and black water tank ?'s

Ok guys I am now in the tank phase of my trailer conversion. I have a few questions:
Fresh:
I have a fill port with the gravity feed and the water hook up to fill the tanks. Do you make 2 different ports in the fresh water tank or you do "Y" these 2 together and run into one port on the fresh tank?
I will be using this as my fresh tank

Gray:
1) Can I use this for my gray tank? It is the perfect size and its ABS. I like ABS as I can use solvents on it to weld the fixtures

2) Where do you guys have your shower and sink draining into the gray water tank? Do you go into the top or into the side. I do not want to go into the top as I will have to drop the tank more.
Black:
Do you guys run your pipe under the frame or do you drill through the frame and run the pipe through the frame?
thank you for your time and insight
Chris
Fresh:
I have a fill port with the gravity feed and the water hook up to fill the tanks. Do you make 2 different ports in the fresh water tank or you do "Y" these 2 together and run into one port on the fresh tank?
I will be using this as my fresh tank

Gray:
1) Can I use this for my gray tank? It is the perfect size and its ABS. I like ABS as I can use solvents on it to weld the fixtures

2) Where do you guys have your shower and sink draining into the gray water tank? Do you go into the top or into the side. I do not want to go into the top as I will have to drop the tank more.
Black:
Do you guys run your pipe under the frame or do you drill through the frame and run the pipe through the frame?
thank you for your time and insight
Chris