"I use the flimsy 24 or 15 section trays which sit in sturdy trays."
Same here, Tony! Over the years I've bought 30 trays with 15 square pots per tray, and at 6gms, are pretty flimsy, but when the tray is loaded up, they lock up incredibly well! They also have a tiny reservoir in the base of the tray which helps on dry days. Some trays here are about seven years old!
I think you might be happily surprised, Wellington, if these are the types you've ordered! I've never broken one at all, as just a small squeeze releases the seedling, and away you go!
They're great for toms, runner beans and sweet peas...