Your sixty minute HGI indicator looks really good on the 15 minute. I do not know how much more tuning you could do and it would be more cosmetic probably to some degree maybe but I would not have any trouble trading this 60 minute indicator on the 15 minutes with a litlle volume and linear regression as it is right now.
The 60 minute time period with 24 intraday candles is an intraday time period in my way of thinking. So if you can catch most of the moves there you will also be picking them up on the 15 minute. The 60 minute 2:1 works just fine on the 15 minute to pick up just about all of the counter trend moves. So it is not surprising to see your 60 minute indicator adapting itself to the 15 minute fairly well.
It is fascinating to see how HGI switches into range arrows as the linear regression channel shows a range.
For those not familiar with volume indicator. Those big white bars on the volume indicator will signal a down trend and than later an end to a down trend and sometimes in between more steam to a downtrend. The red one do just the opposite. You do not always get them but when you do they are killer signals.
Tommaso if you could make the color of the arrows user select-able that would be really nice. I have failing vision and those dark color green arrows I just cannot see. Every time I change them to aqua and make a template they go back to dark green.
Sorry Tommaso SWG gave me a brain transplant below in another post. 
This is really close and if you throw out the low volume periods of the day this 60 minute HGI indicator is not missing anything much on this chart. I looked at every pair.
