The thought that the helical will cause too much speed loss: This is really a misnomer, at least for standard hunting distances. With 4" helical feathers, my arrows would shoot within about 1" of the POI of an offset feather fletch out at 35 yards or so. Beyond that the drop of the helicals becomes much more prevalent as they slow down faster.
I disagree with a few points here.
That "35 yards" stuff is a myth. For field archery competition, where targets ranged from a matter of a few feet out to 80 yards, I usually used 5" helical feathers in good weather. In wet weather, I used the sameexact arrows, onlyfletched with 5" straight vanes. These arrows all shot and grouped exactly the same, with the exact same sight settings, even on the 80 yard targets. If there was any tendency for drop to be more prevelant beyond 35 yards with helical feathers, they wouldn't be grouping together with straight fletched vanes at 80 yards. Myth busted.
Now, for broadheads, I'd never shoot straight fletch. Helical or offset only.
A prong rest does limit the amount of helicalyou can use per length of the fletching, but there is no problem achieving clearance with it properly set up and the arrows properly fletched (unless you use those really skinny carbons, that is). In fact, custom fletching your arrows to resolve your clearance issues is a perfect reason to learn to fletch your own arrows. But I guess I'm one of the few diehards that still uses a ancient prong rest. Everyone else seems to be using biskits or dropaways.
As long as your broadheads spin true, and you've got quality arrows that are straight and consistent, there is no reason to be forced into using mechanicals at higher speeds.
And that stuff about 'notable loss of velocity' with helical is pure meadow muffins. The only way that can happen is if someone just went absolutelywild with the helical and used way too much, to the point where they wound up with a barber pole effect, making more of a parachuterather than just stabilizing wings. Practice moderation with helical and you'll be fine.
Blazers... I don't think they are much lighter than 4" vanes. They're shorter, but thicker, stiffer and higher profile. So don't look for a big speed boost if you switch to them. They are excellent performers though and because of the shorter length, you can do a healthy offset or helical with them.With a good offset or helical, they'll do every bit the job a 4" vane will do. Many folks prefer them to 4" vanes, as do I. Their durability is what got my attention.