For singles it's not a problem. I've actually done considerably more than what you have on Friday. As long as the intensities are high and the volumes are very low it can be quite advantageous.
i spoke to coach that agreed during such things could help but he said they were just too risky esp if the coach didn't have experience at during such things the day before. i think the key to during high int work the day before a meet is you must do nothing or lite work on thursday.