I recently bought some new batteries, and did look at the LiHV ones from HobbyKing as they were cheap.
In the end I went with 7.4v for a number of reasons. 1. I felt it would be cheating if I charged to the full 7.6v, the temptation would be there just to see if it would make any difference. 2. I didn't bother to check if my chargers can charge LiPOs to 7.6v. 3. If the charger did charge to 7.6v, the probability of me overcharging existing batteries would go up which would be a big problem given my teenager also charges batteries. 4. HobbyKing had a sale and the 7.4v graphene batteries were on special offer.
Not sure if this answers your question. But maybe give you some things to think about. I'm sure I read somewhere as well that BRCA were going to allow LiHV as long as they were only charged to 7.4v, but that's just another thing they would need to check before a race starts.
Yeah I looked before there is now a selection on BRCA hologen. april 2017 list. Looks like you need a LIHV compatible charger, I don't think you can charge them on Lipo settings. I haven't looked into speedos yet but might need a compatible one.
I just don't want to buy lipos then a few months down the line everyone starts moving to LIHV batteries .
Looks like there is a small amount of performance increase but it doesn't look significant just might have to wait and see.
LiHV should be charged on lipo settings. But most chargers will cut off before reaching full capacity for LiHV (overcharging lipos often means you get a fire to contend with). This is why balance charging is important, it ensures that each of the cells in a 2s battery is not overcharged.
So you need a charger where you can increase the "fully charged cut-off". And this means if you then charge a normal 2s lipo, you need to remember to reduce the cut off (or live with the increased chance of the batteries going on fire). I've spent a lot of time explaining to my teenager why the balance change mode exists, and to make sure he uses it.
Maybe this is a question for the "rule makers". A quick search and I found the following text "normal racing regulations allows up to 4.2v".