I also agree on the point that RG version feels superior in a way. My approach is the following:

Maindeck:
4 Wasteland
4 Rishadan Port
3 Bloodstained Mire
4 Wooded Foothills
4 Mountain
3 Taiga

4 Goblin Lackey
4 Mogg Fanatic
4 Goblin Piledriver
4 Gempalm Incinerator
4 Goblin Matron
1 Goblin Sharpshooter
4 Goblin Warchief
4 Goblin Ringleader
2 Siege-Gang Commander

4 Æther Vial
3 Relic of Progenitus

Sideboard:

4 Chalice of the Void
4 Pyrostatic Pillar
1 Tranquil Domain
3 Krosan Grip
3 Pyrokinesis

It plays Mono Red main with 3 maindeck relics (which are a HOUSE in a meta full of Threshold, Loam, and Tarmadecks in general) and offers the green splash for the sideboard. The manabase support disruption lands and you are not forced to fetch for taiga first game as you donīt maindeck any green cards.

Maindeck Relics solve the issue of Tharmagoyf in an awesome way as they not only stop the first one in the short term, but possibly also the following ones later on (which WW does not do). Apart from wrecking Ichorid game one in an unexpected way :D Graveyard using decks are at the top tables more and more everyday.

Green is basically for one of the most versatile sideboard cards right now: Krosan Grip. The lonely Tranquil Domain is a tech against Enchantress, double plague and W or U Propaganda decks. Additionally, 8 slots to fight combo seem enough and might ease the things in case of having to mulligan aggressively for lackey/vial or disruption pieces (depending if you are on the play or not). Playing just 4 slots against combo donīt seem enough. Also, maindecking relics free some valuable space in the side.
Also, as has been mentioned in this thread before, Chalice helps against Burn (if it is present in your meta).

I am thinking of maindecking a Tin Streen (for an Incinerator maybe?).

What do you think?