i've done this even with straight guys and once they get over the awkwardness it is very hot. you just relax into it and grip them together so the underside of the helmets rub together. also hot to go tip to tip so the penises are lined up 'eye to eye'
My preference is the long, skinny one. Too wide (like my own) tires my mouth and makes my asshole really sore. Long, but thin, and I can take it deep in my ass or throat. Also longer can hit spaces up inside my rectum that few guys can.