can the 61/2 " shower head be replaced with a larger rainshower head?A. Yes, you could purchase a larger shower head to with the Grohe GRFLX-T303 shower set up.
you say this has a 2 way diverter function, but that no diverter is included? I don't understandA. The Grohe GRFLX-T303 does have a diverter included in it, it is a part on the control. There will be a button on the top to switch from one to the other.
Is there a way to make this system work in a tub/shower combo with a tub spout?A.
The Grohe GRFLX-T303 can be used together with the Grohe 13 603 diverter tub spout.
Can the Grohe GRFLX-T303 hand shower be installed without the bar?A.
The Grohe GRFLX-T303 can be installed without the bar; you would need to purchase a holder for the hand shower head.