The 17-year-old admitted that the young squad were up against it from the start in a tournament studded with stars of the sevens world but added that the experience is something the entire group will take forward with them.
"We've played against some good, mainly sevens teams who are a lot more organised but I think at times we stood up well," the fly half told SaintsTV.
"It's a great experience playing at Twickenham with all your mates and we've had a really youthful squad out. Results may not have gone our way but I've really enjoyed it and the chance to play against superstars like Carlin Isles and co."
It's been an unforgettable weekend for Mallinder, who fulfilled every young rugby player's dream of walking out at the home of English rugby less than 24 hours after linking up with the Saints squad for an assured first senior appearance in the friendly win at Goldington Road.
"I was excited and a little bit nervous in that first game [at Twickenham] even if there isn't a full house here. There are still a lot of people watching and you want to impress, especially when the TV cameras are on you too!"
"Friday evening was maybe even better," he added. "It was a great experience and in front of a good crowd at Bedford and a good atmosphere. I really enjoyed the 20 minutes or so I got and I'm already looking forward to hopefully a few more.
"It was very interesting in the changing rooms. I had Courtney Lawes one side of me and some of the Academy lads the other side but they all looked after me and it was good fun.
"I've learnt a lot from this weekend's experiences along with the rest of the Academy lads and hopefully we can take that forward into the rest of the season."
A valuable weekend for the young Saints then, even if they will be keen to forget a difficult two days of sevens action.
Having missed out on a place in the last eight by a single point on Saturday, Sunday started with a Shield semi-final defeat against the sevens specialists of Krasnodar - the Russians breaking the deadlock with 90 seconds to play in the first half and then delivering the fatal blow by doubling their lead well after the hooter.
Staring down a 14-point deficit, Saints came back out and threw caution to the wind but a third from Krasnodar's Stanislav Bondarev soon made it 0-21 thereafter and though the Saints monopolised possession, an organised opposing defence refused to cede any ground or points for that matter.
That meant one final clash with Western Province and after snatching the lead against the run of play, the South Africans extended their advantage on the stroke of half-time.
Even with a man in the bin for a deliberate knock on, WP continued to expose an inexperienced Saints seven and another quartet of tries ensured the Saints' World Club 7s campaign ended in frustrating defeat, even with Mallinder giving them the final say with his first try of the tournament.
Danny Hobbs-Awoyemi, Ollie Lyons, Paul Diggin, Alex Day, Harry Mallinder, Jacob Conner, Sam Harry, Harry Betts, Ryan Glynn, Tom Collins, Vasily Artemyev, Tom Stephenson
DAY TWO RESULTS
Saints 0-21 Krasnodar
Western Province 31-7 Saints