I would say the partial mannequin from the waist down to just above the knee area would be a no brainer for this set, however if your looking to display the cowl with then then I'd invest in a full mannequin which can be bought for a hundred bucks or less on eBay and other retail sites, not to mention it's got a head to display the cowl as well as the belt and holsters with pistols... If you've already invested in the belt and holsters, pistols, and the cowl then why not go one step further and buy the full costume since it's cheaper then the parts you've already invested in and now you have everything and a full size mannequin is the best way to display your entire collection..
Now with a collection like mine it's more difficult to display my belts and holsters and all that stuff because I have maybe twenty to thirty belts and holsters and bandoleers from Gene Roddenberrys Andromeda and I don't have the availability of all the costumes to go with all of my belts and holster sets so it's a bit more of a challenge to display them all separately or with the correct costumes.... So with my collection I mount as many as I can with the original costumes that I do own and the rest I made a big display board that's mounted to the wall and then the belts and holsters are mounted to it with some sword mounts that can be bought at a number of different sites and they are displayed as they would if you were to lay out the set flat on the ground and they do require a lot of room this way so it took up two complete walls because of the sheer amount that I have.... Anyway if you want a lifelike display then invest in a mannequin and the spandex costume and a decent mannequin and make it a complete set and it'll look amazing... With my andromeda collection I already have 14 complete screen worn costumes mounted on mannequins already and the costume portion of my collection is still growing all the time so by the time I'm done I'll have maybe thirty or forty complete costume sets displayed on mannequins but I do still have other costumes from Stargate SG1, SG Atlantis, and The Lord of the Rings so it's a massive collection that is ever evolving and constantly growing so in the end I'll have a lot mor to worry about displaying so good luck
Bill