Welcome to my easy mod guide for Rhino Prime.
Try it and then Adjust to your Game-Play later!

Content:
1. My build.
2. An Endgame build.
3. The Game-Play wanted!?
4. Iron Skin Synergy Augment Mods.
5. The way I use this.
6. Last words.

Before we jump into explanations on How Iron Skin and Effective Health works, lets take a look on this build.

1. My build:

(Armor shown above, on this site, is 648 since the Aura mod is taken into account;
Where [Stand United], 25.5% of 275 = 70.125 and 577 + 70.125 = 647.125 but lets do the math taking only 577)

Armor: 577 Duration: 128%
Energy: 425 Efficiency: 100%
Health: 740 Range: 100%
Shield: 450 Strength: 170%

Since The Armor and Health works Together, we need to know how much Real Life (Effective Health) we have.

Effective Health: 2163
( (577/300) +1 ) x 740 = 2163.26~ Effective Health
The Effective Health Formula: ((Armor/300)+1) x Health = Effective Health

Iron Skin Energy Drain: 50

Iron Skin Health (Absorbed Damage): 4492.25 (In Game Stats)
(1200 + (2.5 x 275 x (1 + 110%))) x (1 + 70%) = 4494.375
2643.75 x 1.7 = 4494.375
The Iron Skin Health (Absorbed Damage)Formula:
(Base Health + (Armor Multiplier × Base Armor × (1 + Armor Mods))) × (1 + Ability Strength) = Absorbed Damage

2. An ENDGAME build:

(Always and again a question of compromise!)

THE ENDGAME [Rhino] Build:
A popular build of [Rhino], Without speaking of its 'Specific' goal, goes with theses basic stats:

Armor: 275 Duration: 171%
Energy: 150 Efficiency: 45%
Health: 300 Range: 79%
Shield: 450 Strength: 337%

Effective Health : 575
( (275/300) +1 ) x 300 = 575 Effective Health

Iron Skin Energy Drain: 78
(or 50 + 55% = 77.5, round up to 78 since efficiency is at 45%)

Iron Skin Health (Absorbed Damage): 6360
(1200 + (2.5 x 275 x (1 + 0 (No Armor Mods used)))) x (1 + 237%) = His Absorbed Damage.
1887.5 x 3.37 = 6360

3. The Game-Play wanted !?

So now I ask you, if your energy is full, with both builds offering a shield of 450,
how would you prefer to cast the Iron Skin to feel safe?

My Build = 8 x 4492.25 buff + Effective Health @ 2163
(8 cast with 3 seconds of invulnerability, so 24 seconds of inv. total. +3 augment mods)
Or
The ENDGAME = 1 x 6360 + Effective Health @ 575
(1 cast with 3 seconds of invulnerability and no augment mods)

I would go with my build if you ask me, period!

4. Iron Skin Synergy Augment Mods!

It will be very easy for me to talk about the ENDGAME build since there is ZERO augment mods on it (Palm Face). But no worries, we will use them to make Rhino Shine !!!

1. IronClad Charge / This is the Deal! Boost your skin.
2. Iron Shrapnel / Allow you to Recast your skin faster and Hurt enemies.
3. Reinforcing Stomp / Able to Repair your Skin... Try Me!

The [Reinforcing Stomp] mod is not where the beauty of the Iron Skin lies but still nice to have.

When you start a mission you might be tempted to just press 2 a.s.a.p. but just DONT yet.
First use your [Ironclad Charge] mod by pressing on your 1,
you will then have 10 seconds ... to activate your 2 and get an Higher Iron Skin health.

Once you have a higher buff because of this (1 then 2), if you want, press on 2 again to deal 100% of its remaining Health as Puncture Damage.

Another way of getting an higher Iron Skin is to use the 3 seconds of invulnerability when activated. Simply put, Cast your #2 then don't kill anything, You want to be hit by anything in fact for 3 seconds~, every damage you absorb in this short period of time will be added to your Iron Skin health.

Lastly take a look on some arcanes to help you maximize this ability. Arcane Tanker on your Warframe is a must, equip your Archgun and press 1...then 2. Arcane Guardian and Ultimatum are too a must try. Other nice Armor Mods: Armored Agility/Health Conversion/Umbral(s)...

5. The way I use this:

Deploy my archgun (with arcane tanker) = +1200 armor for 60 seconds. Use IronClad for a shorter than 10 seconds period, lets say 3 or 4 times, to hit more enemies.
Finally press 2 and try to be hit by enemies for 3 seconds.
If happy with the value obtained... will use Reinforcing Stomp to keep it.

6. Last words.

At the beginning of each public mission usually Its hard to hit a lot of enemies with your first ability since everybody is killing them fast. So here just try to get 20k~ armor... and later with more enemies try to go for 40k~.
Once you'll be familiar with this method you should be in the 50k-100k with no problem at all.
It is really up to you to go higher but IMHO its useless...

Hope you will now be able to mod correctly for what you need to accomplish using [Rhino].

Now you understand why the 'Effective Health' is defined by the amount of 'Health and Armor', to know how much 'real life' we have.
((Armor/300)+1) x Health = Effective Health

To define the [Rhino] Iron Skin value, we only need to play with 2 things, the Armor mods and Ability Strength.
(Base Health + (Armor Multiplier × Base Armor × (1 + Armor Mods))) × (1 + Ability Strength) = Absorbed Damage

Adjust your basic stats to your Game-Play and have fun.

All the best to you Tenno!

This post is a work in progress.
Please like if you learned something!
Thank you!