I was passing by & went in for a day trip first week of May & it was pretty bad. 

I spoke with the ranger who said their usual grader driver had a stroke & the road hadn't been touched for months, didn't sound like they had any one else lined for a while either. 
 

id be keen to see your thoughts once you've done it as we're heading back up late July.

the useless loop road was really good & they were doing work to the road. I dropped to about 28psi at the gravel & sat on 80-100kmh all the way to the ranger pay station. As soon as you get to the end of useless loop rd & turns into national park (pay station) I'd drop straight down to 15psi. On the way in I tried different speeds but some sections were shocking & had me back down to crawling speed. On the way out the poor cruiser coped it and sat on 60-70kmh which was ok, short term pain. Got lucky with traffic & pretty dangerous with a few sections/corners I must admit at that speed... but it's either that or be prepared to hate life for the next few hours 

towing a trailer I would allow a fair bit more time unless they've graded the track