The MAHA ratified the player registration rules put in place by the CAHA to maintain amateurism and exclude professionals, and sought to expand within Manitoba by recruiting existing leagues to join.

[17] A letter by him was published in the Winnipeg Free Press, in which he reiterated his commitment to expanding senior ice hockey in Manitoba, and restoring it to the prominence it had before rosters were depleted by professional teams.

Gilroy advocated for support of leagues based in rural areas to grow interest in the game, and since those teams could not raise funds to travel long distances to play in larger cities.

[19] As growth increased, he sought to educate teams and players in Manitoba that registration requirements including transfers between clubs would be enforced in the 1928–29 season, and published letters in newspapers advising of changes to consistent with new amateur regulations across Canada.

[20] The MAHA implemented upper and lower divisions in the Manitoba Senior Hockey League for the 1929–30 season, and received more applications from teams in Winnipeg than ice availability could support.

[27][28] He was immediately faced with an ultimatum from the north division teams of the Manitoba Junior Hockey League (MJHL) who threatened to withdraw from the MAHA unless several demands were met.

[27] The teams felt that the south division was given preferential treatment, and sought to equally share games at the larger Winnipeg Amphitheatre and the profits from gate receipts.

[27] The Winnipeg Tribune reported that the concerns had developed over years of mismanagement and that Dunn committed the MAHA to discussing issues openly instead of closed-door meetings without the local press invited.

[33] The Winnipeg Tribune felt that these teams had pursued their own selfish interests with disregard for the general welfare of the league, and that creating the division would perpetuate the previous issues unless Dunn could negotiate a "minor miracle".

[41] The Winnipeg Free Press wrote that Dunn's presidency coincided with the MAHA's biggest growth and best financial situation that was driven by profits from the junior ice hockey playoffs.

[44] Five years later, the MAHA had grown to be the country's third largest provincial association by registration and spent more per capita to develop minor ice hockey than other provinces in Canada.

[47] When the Brandon Wheat Kings also wanted to play in the SJHL, the MAHA renogotiated the financial arrangement to prevent the loss of another team to an out-of-province league.