Hey Glen,
Oddly enough I have used SPM banana ended cables with my vt100m2 - they worked fine.
Do your banana ends have this opening along the cylinder side of the banana that allows the 'cylinder' of the banana to compress & make a thinner cylinder? If this is the case, the intention of the nordost banana plug is to have a spring loaded cylinder that 'spring expands' against the enclosing walls of the speaker/amp terminal.
You do have to use 'moderate' pressure when inserting the speaker cable end into the amp to get this cylinder to compress.