Table topping PGG Wrightson/Balance Taihape have strong representation with 12 players chosen for Country, including the entire backline with the exception of Tom Wells, who will be assistant coach of Country under Ruapehu's Andrew Evans.
Waverley Harvesting Border have been split with seven players turning out of Town, coached by Jerome McCrea and assistant Cornel Mason, and three more Border men in the Country lineup.
While fudging the boundaries a little, Caskey said they wanted to get a competitive mix across the teams, and did not rule out having players swap to the other jersey during the game, as happened in last year's trial in Hunterville.
"We want to see a good game of rugby - a close game.
"But that's why we name a pretty big squad - if anyone can't make it, we can cover them.
"It's really on the players to have the onus to front up."
It will also help with car pooling to practice to have a few guys from each club in different teams, he said.
Obvious vacancies in the Wanganui lineup include first five with Stephen Perofeta now off making headlines with the New Zealand Under-20s.
Taihape's 2014 incumbent Dane Whale will be preferred by Caskey as a No10 despite playing fullback for his club, and the communication skills of Dave Hoskin Carriers Marist veteran Steelie Koro are most prized - provided his leg injuries can come right.
While hooker is relatively set, the ten or so props chosen to trial can stake their claim with Kamipeli Latu overseas and Brett Turner having left town.
"There's a least one [front row] position up for grabs and possibly two," Caskey said.
The outside backs are also worthy of attention and Caskey wants to make sure that Samu Kubunavanua and Michael Nabuliwaqe have not let themselves go since the move to Settlers Honey Ngamatapouri, who as expected are running roughshod over the Senior competition.
In addition, Ngamatapouri's other Heartland reps Malakai Volou and Bryn Hudson have been placed in the opposing loose forwards.
"With the boys from Ngamatapouri, you really want to put them in the trial and play rugby at a higher level," said Caskey.
"Where you go for work is fine but you have to be honest about it - that they're playing at a weaker level."
Another name from outside of Premier rugby is young fullback Te Rangatira Waitokia, who has been turning a lot of heads for Wanganui Metro in the Manawatu Colts competition.
Last year, there were 43 players of the 68 invited who turned up in Hunterville for the Monday game, despite the fact they did not have Premier rugby on the Saturday.
This year, the players will have to front back-to-back, although Caskey pointed out they were young men, and in his playing days, Wanganui had club rugby on a Saturday and first-class fixtures on a Monday against opponents like the full Taranaki team.
"You didn't mind doing it - when I was playing you wanted to play as much rugby as you could.
"If they can't front, they do our job for us and cross their own names out."
The June 6 match will have a 1pm kickoff at Kaierau.
Trainings will be loosely planned for Wednesday's and will be announced on the WRFU Facebook page.
-Those invited are:
Town
Forwards: Viki Tofa (Marist), Hamish Mellow (Border), Tietie Tuimauga (Border), Tolili Moala (Pirates), Jack Yarrall (Kaierau), Dylan Pearce (Border), Joe Edwards (Kaierau), Aiden Fitzgerald (Marist), Meni Taufaasau (Pirates), Jack Hodges (Border), Josh Lane (Kaierau), Lake Ah Chong (Marist), Ryan Gill (Marist), Lasa Ulukuta (Pirates), Bryn Hudson (Ngamatapouri), Fiatau Faalili (Kaierau).
Backs: Rory Gudsell (Marist), Anaru Saurara (Kaierau), Steelie Koro (Marist), James Forsythe (Border), Tevita Tui (Marist), Kaveni Dabenaise (Border), Kameli Kuruyabaki (Kaierau), Meki Magele (Pirates), CJ Stowers (Pirates), Tom Symes (Border), Cameron Crowley (Marist), Simeli Koniferedi (Marist), Te Rangatira Waitokia (Metro Colts), Tupu Tavae (Pirates).
Country
Forwards: Karl Parker (Ruapehu), Richie Iorns (Taihape), Jason White (Ruapehu), Hadlee Hay-Horton (Taihape), Gabriel Hakaraia (Ruapehu), Rimu Wipaki (Taihape), Jake Anderson (Utiku), Archie Toseland (Utiku), Johnson Hiroa (Taihape), Sam Madams (Border), Campbell Hart (Ruapehu), Tremaine Gilbert (Taihape), Jamie Hughes (Ruapehu), Malakai Volou (Ngamatapouri), Hawea Meihana (Ratana), Jake Alabaster (Border).
Backs: Kane Tamou (Ratana), Brett Nicholls (Taihape), Dane Whale (Taihape), Te Tua Kemp (Ratana), Troy Brown (Ruapehu), Cyrus Paringatai (Taihape), Jaye Flaws (Taihape), Brett Illston (Taihape), Sefo Bourke (Taihape), Samu Kubunavanua (Ngamatapouri), Rewi Hudson (Utiku), Taylor Transom (Taihape), Nick Harding (Border), Michael Nabuliwaqe (Ngamatapouri).