*PLUMBERSSTOCK EXPERT* responded:
Hi, there! Thank you for asking us. One of my concerns for the installation that you're proposing is the compatibility of the existing trim you have with the new 3-hole rough-in that you're getting. Most trim kits require s specific rough-in valve for it to work. I'm also concerned about where you will install the Delta RP14979PB handshower. Based on what you said, you own a 3-hole Roman tub and if you're planning on re-using the old trim that you have, there will be no place for the handshower to be installed on (it also requires its own valve to work - namely the Delta RP18632 transfer valve). One of the solutions that I can suggest would be to provide us with the make and model number of the trim kit that you own so that we may be able to find the specific rough-in for it. As for your tub, you can either drill another hole or purchase a new one that can accommodate both the 3-hole trim kit and the handshower. If I've made a mistake on my tub assumptions and you're using a 4-hole Roman tub, then please disregard the tub suggestion I've made. For additional questions and product inquiries, please feel free to ask us again here at PlumbersStock.com! Thank you and we hope to see you again!