McKinstry worked on many prestigious projects including the restoration of St Anne's Cathedral, the Crown Liquor Saloon, the Arts Council of Northern Ireland Gallery, and the Grand Opera House, Belfast.
[2] At the age of seventeen McKinstry sought out and visited the poet Richard Rowley at his Newcastle home, where he was well received and spent a considerable time discussing poetry, the linen industry, the artist George MacCann and the Group Theatre.
When, in 1968 CEMA's successor the Arts Council of Northern Ireland found a new gallery space on Bedford Street in the City, McKinstry was once again appointed architect.
His designs included huge moveable partitions and sliding screens that allowed for a flexible exhibition space and received much international acclaim.
[13] McKinstry completed a two-year restoration of the Shambles Art Gallery in Hillsborough, County Down in 1971 at the behest of the artist Patric Stevenson whom had used the old stables for exhibiting for a number of years until they had deteriorated to such an extent that they could no longer be safely used.
The restoration took four years and included a full modernisation of the backstage areas, a larger orchestra pit and a new fly tower, in addition to improved lighting.
[17] The Ulster New Zealand Trust began renovating Ballance House, Glenavy in 1990, when the appointed architects were Kennedy & Fitzgerald with McKinstry serving as advisor.
[18] McKinstry was later invited to curate an exhibition showing works from sons and daughters of noted Ulster artists and architects at Ballance House in 1998.