Re: Any sage VXP users here?
I've got a VXP 9'6" 8 weight and fish mostly streamers/wets with it, so you may not find this useful. I fish mainly for salmon and steelhead and use a Rio Versi-Tip 8 weight line, usually with one of the heavier sink tips attached. However, I've fished it with everything from the floating tip to the Type 8 sink tip, and agree with your assessment: it's a sweet casting and versatile rod. It can definitely handle heavy tips and big flies, and land big fish, with no problem. With it I've caught coho of 15+ lbs, my first steelhead, and this past March my first bonefish in Belize. In the salt I used a 8 weight Rio general purpose tropic line and liked it, although next time I might upline to a 9 weight.
It sounds like you're using your 5 weight for very different kinds of fishing, so I'm not sure if this will offer any insight. For what it's worth, I think it can handle a heavier taper/line.