The first time I looked at a 4x5 velvia 50 slide, I just about dropped to my knees wondering why I shot digital for so damn long.... I regularly look at 4x5 and 6x12/6x17 slides and think to myself... This is it. Photographic ecstasy.
The idea of a 7x17 RVP50 slide almost brings tears to the eye... You would literally just frame the slides with a backlit panel behind them... And they would be pure awesome.