Clubs are preparing for a second week of action undertaking the amendment which altered the definition of a high tackle from above the line of the shoulders to above the armpit line.
Doncaster, who head to Nottingham tonight, beat Coventry 20-19 in their inaugural Championship Cup tie last Saturday when both sides experienced the law tweak for the first time.
The trial, staged over all 43 games in the pool stages and play-off rounds of the competition, has multiple aims.
Namely, to assess the impact of introducing a lower tackle height in elite adult rugby on the incidence of concussion and other injuries; player behaviour in the tackle; the nature of tackles; head injury events and other game events.
A detailed analysis will then be compared to existing data from the English professional game to help inform any wider approach.
However, Doncaster’s skills and backs coach Cooke told The Yorkshire Post that the initial findings from the first round of games had been enlightening.
“Beforehand, we showed the players some footage of tackles made earlier this year that would have resulted in red or yellow cards under this rule,” he said.
“I think that surprised them. But the tackles have got to get lower. It’s as simple as that.
“And we’ve had some interesting feedback. The figures are fascinating. This season, on average, there’s only been six penalties per week for high tackles in the Championship. That’s less than one per game.
“So, when the refs came into advise us, my question was why are we looking to enforce this change to the high tackle if the numbers are so low anyway?
“Why are we tinkering with the rules? But, as was reminded to us, it is a World Rugby directive which is being trialled in the Championship Cup so we just have to go with that for these next few weeks.”
Cooke continued: “Against Coventry, we had six penalties for high tackles in the first half and four of those actually came from outside backs.
“They are a bit more isolated on the edge and more likely to hang out an arm – there’s more one-on-one contests in that area – whereas in the middle of the field I don’t think we saw any given.
“There’s more grappling there and more numbers in the tackle and that’s been the reality. We showed the players at half-time and reminded them that they had to get their bodies lower. But I worry for the tackler rather than the attacker; I feel the tackler is going to cop more hips, boots and knees by tackling further down.
“Us, as coaches, have to work on that to make sure it doesn’t happen. But someone like (Knights lock) Matt Challinor, for instance, with the way he runs, could knock a few people out if they have to go low on him every time. It’s something to look at.”
As they seek to reduce concussion risks and improve player welfare, the RFU has already had a clampdown on high tackles this season with a series of highly-publicised and controversial dismissals for collisions which would not previously have warranted a card. However, for those playing in the Championship Cup (group stages run until December 15) the chances of facing such punishments naturally increase.
“The hard facts are over the next five weeks that’s how it’s going to be ruled,” added Cooke.
“If you don’t get your body position right then there’s no getting away from it; there’s going to be more red and yellow cards handed out.
“It’d be unfortunate if any player gets a ban the week before the return to Championship action; we don’t want to see players missing that game with Yorkshire Carnegie on December 29.
“But it works the other way, too, in that Carnegie could see players suspended for that fixture as well.
“I do think, though, the refs are trying to referee with some common sense as well.”
Meanwhile, Doncaster director of rugby Clive Griffiths watched the Coventry game at Castle Park, his first live match since suffering a heart attack in September.
Cooke explained: “He’s easing back in and he’s not 100 per cent but you can’t keep a good man down.
“We definitely didn’t let him near the radio but he made some decisions regards substitutions and he knows he has to take things a bit more steady. It’s good to see him back.”
Former World Cup-winning England defence coach Phil Larder, 73, has been assisting at Doncaster during the last few weeks.
Cooke said: “He’s been really good and the players are listening to all his experience; they have to improve as a defensive unit.”