We have the Givi and I was concerned that the back rest was too far forward but my pillion liked it. The next test was long distance rides and low back support which I really thought could be a problem. Nope, just the opposite effect. She feels more secure with all that mass behind her and it allows her more positions to sit and to lean back a bit.

I do think you gotta which the weight in the trunk because even relatively light I could feel the bike's handling was effected slightly.