I know they're out there, I was considering using one on a mountain bike to change the fit. The one consideration on a road type frame is that it will change your riding position by effectively moving the bottom bracket further forward, changing the muscles you use (i.e. more hamstring, less glute/quad). Changing riding positions like this is referred to as "getting your legs", and takes some adjustment getting used to using new muscles. I'd consider changing the fit with a longer stem, instead, providing the same increased reach up top, but keeping your hips over the bottom bracket like they are now.