Haly would accept the Sun as both hyleg and alchocoden given it was in Aries or Leo and in the MC (and maybe the ascendant?). But the hyleg and alchocoden are meant to show vitality / constitution or in other words the maximum life span. The bounds form the constitution whereas the hyleg is the life force. If you have a strong vitality but weak constitution or vice versa, it will shorten that span. Presumably the reason for using bounds as constitution is because a boundary forms a container to hold that vitality in place. One might say that the hyleg represents the spirit and the bound lord represents the soul (in aristotelian terms).
What's missing here is "unless the rays of a malefic should cut the debt [owed to the native] short". In other words, you can be in great health, but if you get run over by a bus... So check the hyleg against the anaretic rays. I prefer to look at these as danger points since there is lots of author disagreement, so I set up the primary directions to look at the main hyleg candidates (Asc, Sun, Moon, PNL, Fortune) and then check malefic rays against all of them (keeping in mind the most likely candidates).
Thanks for your answer! Really appreciate it.
I agree to pay attention to all of Asc, Sun, Moon, PNL, Fortune. But some guys in this post before said hyleg and alcocoden show the least longevity which can be prolonged by modern medical treatment. I'm a little confused. And bounds forming constitution never showed up in this longevity topic!
If my sun can't be hyleg, neither my masculine moon in 1st house. I'm conjunctional, so Asc can be hyleg, which conjucts lord sun. Sun is alcocoden, which conjuncts Jupiter (combustion) and Moon (rays). Sun gives the most longevity. Though Jupiter is combustion and moon rays, jupiter has triplicity and moon conjuncts Regulus and both in first house. I assume they can at least add some yrs.
So my longevity could be 120+? Or even 150+?
Virgo Fortune in 1st house conjuncts virgo Mercury (ruler, joys) and Venus. Can they add some more? BTW, Aquarius saturn in 6th house aspects no planet.