You are only about 1.5 miles out of kirkmichael. Some buses run over the Glen Helen/Cronkyvoddy section but they tend to be closer to road closing times as best I understand. Either way, seeing the bikes come by for a split second albeit for quite a spectacle has never appealed to me. You would need to get there about 3-4 hours before roads close to get a decent view. Have walked past it a few times and there is not much room. You would be squeezed up against a fence the entire time.

My preference is to be close to the action, have a bit of space about me and can see the racers for more than a few seconds at a time. I marshal half the time but when spectating, I like the following;

Ballacraine - just up from corner on the outside of the circuit. Good vantage points always available 30 mins prior to roads close. Set them hammering toward you then trying to keep it under control hard on the anchors before throwing it into the corner. Access via field after road close. Refreshments available. Might have to pay for access through field after road close but I have never been charged.

Greaba castle - viewing available on outside of course on top of wall. Marshals let you sit on recrticel barriers prior to race. Never too crowded. Can see them coming through the left then flicking it right before drifting to outside of track and kissing the recticel barrier on exit. Access via heritage trail and a field after roads close.

Cronk Y Voddy. I much prefer at top of Lambfell / start of cronk y voddy straight. Can see them blast up Lambfell before flying past you and on along the straight. Plenty of room.

Start / finish on inside of course at bus stop. Decent viewing opportunity 2 hours prior. Get to see the build up which in my estimation is the most emotional raw experience of the entire TT (or of anything I have ever witnessed). Watching the riders go through their pre race rituals with their team / loved ones is almost too personal to watch. I just want them all to come back safely. Not the greatest vantage point once the race starts though watching them come past and disappear as they roar out sight while grabbing more gears heading down bray hill defies logic. You also see them come into pits and you are in the heart of the event with a great atmosphere. Plenty of access and refreshments upstairs in the gymnasium centre.