Really any fixed blade head is easy to tune. The manufacturing process's, on a quality head, are so tight anymore that they all align with minimal tuning needed. Most of your inconsistencies is going to come from the arrow end of things. Just some food for thought. You may want to switch your wife to 85gr. as this will open up many more broadheads choices than a 75. Possibly even to 100gr.
I would love to get my wife to 100 grains and shoot the same broadhead but I shoot 68 lb 30" and she shoots a 30-40 bow currently at 36 (and rising as she builds strength - we hope to be at 40 by October) and most folks recomended a small diameter lighter broadhead for PENETRATION - so we have the Muzzy 75's because they are only 1" and are said to penetrate. Having said that - we have not shot them yet and if I have a tuning problem I will need a backup plan - and that is the point of this question. I, on the other hand, have tons of options and can expect to get full penetration with most broadheads so tuning will be the only outstanding challenge for me.
I should have emphasized this point....... IF I have a problem with my wifes' 75 grain muzzies I won't know it until I have just weeks before our trip with an outfitter in Ohio. The reason for the potential timing squeeze is that she needs to get up to 40 lb before I test the broadheads. I see little value in tuning things at 36 lb then raising the pull to 40 or 41 lb and re-doing the tuning process. So everything may work well for her - but if I have a problem it will surface with minimal time to resolve so I am building my backup plan now.
I'm sure it is a little late in the process to change things now but a heavier arrow with a good FOC will have more effect on penetration ability than a small diameter, light BH. I would go so far as to suggest that a light BH has a detrimental effect on penetration. As Backcountry suggests, most tuning problems seem to be related to the arrow, or poorly built (with regard to FOC, weight) arrows, than the BH used. From what you have said it sonds as if you have little choice but to use the 75 grain muzzys at this point. I would start the tuning process now, even at 36#'s, to see if there may be some corrections that need to be made. You likely get a good idea of what you need to do at 40 #'s while you are still at 36#'s. Hopefully you willbe shooting a little stiff at 36. Even if they tune stiff at 40#'s you may still be OK if your wife's effective range is not to long. IMO it would be better for her to be shooting a stiff spine at shorter ranges.
She is shooting a stiff spine PSE 200 Radial Weave Carbon Hunting arrow (different scale from Easton just to confuse us in comparisons) at 26.5" overall length. The pro shop went on the stiff side because they unerstood the goal was to kill a deer not 3D targets.
Sounds good. At that spine you are probably good to go with a heavier BH (even up to 125grains) if you wanted to. I would start the BH tuning process now. There probably won't be a big difference in things from 36# to 40# except maybe adjusting the sight pins a little.
Idealy, if your bow setup is tuned properly you shouldn't have much trouble using about any broadhead fixed or mechanical. Broadheads have a way about bringing out the worst in your bow so it's critical to make sure everything is adjusted well especially when using fixed blades. You can't always see this with field tips so it's always best to test your broadheads and go from there. I would say to pick out a brand and style and tune the bow to it. There are dozens of good broadhead makers out there so your chances of choosing a good setup are high.
