Disclaimer: I'm not the best at math, so this could be wrong and if it is, I'll fix it.
from a mathematical standpoint, go with the last corral/sweepers starting at 6am and the sweep line being 3.5hrs, that means around 9:30am at the finish line. It would also completely depend on what the actual park hours are on that day. It would probably depend on where HS ended up being on the course, your pace, etc. if you could get on a ride for the half. Last year it looks like HS was around the 10mi mark (160min OR 8:40am) and the options would be ToT or RnR for rides. That would give you a maximum allowable time of 50min to finish the race AFTER getting off the ride (16min/mi for 3.1mi.) For some people that is more than doable, and for others it may not be. How long will the line for the ride be? How long does it take to get through the queue and onto the ride and then back actually GO on the ride and get back on the course? It would also depend on where they would be making the actual sweep points on the course since if you DID have to wait until 8:30 to get on the ride, the sweep line would be entering HS at around that time as well (8:40am ish.) And from there you have to weigh the risk/reward of going on a ride during the half and potentially getting swept because you stopped (and the line was long, there was a technical issue, the pre-ride area takes a long time, etc) and then they swept in front of you before you were able to catch up even if you would have been able to catch up.
During the full marathon in January there's more wiggle room and I believe most people who go on rides do so much later in the race (and when the parks are open) in AK and HS because they're close enough to the end that the park is open by the time they get there, but they still have plenty of cushion time in front of the sweep line.
