I say go for it. Will you be blogging? (That would really impress!)
This year, in May, I met a German pilgrim named Peter who walked from Fromista to Moratinos (9 km before Sahagun) in a single day. I remarked to him that must have been close to 50 Km. He said 51. He then remarked that he wanted to make Sahagun that night (60 km total) but is was already nearly dark and he needed a place to sleep for the night.
In any event, he was doing this because he only had a limited amount of holiday remaining to finish and he was doing it for a noble purpose, as he explained. But, Peter did admit that this was his most difficult day yet, and that his feet and knees were bothering him.
BTW, Peter was about 190 cm tall, of thin to average build, with very long legs. He was muscular and appeared to me to be in very good physical condition. He was also a well experienced distance hiker / walker. But he did appear to be physically exhausted. He departed early the next morning.
My point in mentioning this experience is to point out that doing 50 km or more in one day is technically possible, especially on rolling and level ground like the Meseta between Fromista and Moratinos or Sahagun. However, sustaining this pace on hilly terrain (Navarra or Galicia), and in possibly bad weather is another thing entirely.
Have you ever walked the Camino in constant, driving rain? I hate mud! After two Caminos I can safely say that I prefer being wet, to being wet and muddy. But along the Camino, unless you are road walking, mud is a certainty. You just need to deal with it. Mud also reduces an hourly pace nearly 50 percent. So, a 5 km per hour pace becomes 3 km/hour or less.
For the record, the day I met Peter, it had been sunny, cloudless, completely without rain, and about 22-23 degrees Celsius at midday. In other words, what some might consider a perfect day for the Camino. And by Peter's own account, walking 51 Km that day was pushing it, but he felt he needed to to accomplish his noble purpose. I can respect that.
Personally, I make better time on a cloudy, but dry day. But, for me, it is not about time, but about space. I enjoy the view, the scenery, the animals, flora, and people, old buildings and everything else visual, aural, or tactile.
In the final assessment, you must do what you think best, as it is your Camino. Those of us who are more or less "happy hobos" along a Camino would appreciate it if you either wore a cowbell or announced your overtaking us rapidly (call out "passing on the left" or "on your left"), so we can step to the right side and allow you to pass on our left. As you will quickly be out of earshot, please allow me to wish you a sincere and heartfelt "Buen Camino" in advance.
I hope this helps.