Try the gloriosa X glauca both ways since the offspring will be different. I would assume the pollen donor will pass much of the leaf traits. So Y. glauca x gloriosa may produce larger, trunking specimens?? Either way, both crosses sound great.
It looks like I'll have Y. recurvifolia 'highway 421' seed. This Yucca survived 'the winter from hell' as many forms were killed above the snow line. This is the only trunking yucca in my garden with ERECT seed pods. All others have pendant seed pods. You need to try this form for hardiness.