OK, gang, today's study question:  How much gel does it take?  I've been investigating various add-ons and most cushions, etc., seem to be 1/2" gel sandwiched between two 1" slabs of foam.  More or less.   Doesn't sound like a lotta gel.  Has anyone ever taken apart one of the after-market gel seats to see just what is in there?  Would 1/2" gel and new foam make much of a difference?  I'm a little late in asking, as I am headed  in that direction already, but the suspense is killing me (even as the stock seat is REALLY killing me.)

Gel is used for its viscoelastic properties. It does two things: It absorbs vibration and it helps spread the load out more evenly across the substrate material. At some point, more gel won't do anything for you if the substrate material or topping material is poor. Imagine sitting on a seat made of a concrete block, covered with a 1/2 gel pad, with a 1" feather pillow over it. Might feel good to the hand, but when you sit on it the feathers will compress, the gel will spread out your weight and pretty quickly it will feel like you're sitting on a concrete block.

. The two key things that differentiate foams are density and IFD, which stands for Indentation Force deflection. Simply put, it's a measure of how much force it takes to squish a foam a fixed amount, like to 65% of the original height.  So  a foam with an IFD of 60 takes a lot of force to squish, and a foam with an IFD of 20 is going to compress more easily. People think squishier foam makes a better seat. Not always!

When you sit on any comfy seat the first thing your highly trained butt notices is the initial compression, which makes a seat feel cushy. But, if you keep sinking down, then you bottom out on the base which is painful, So a low IFD foam feels good at first and then becomes a cheap, easily deformed bean bag like thing. On the other hand, a high resiliency foam with an IFD over 60 feels very firm at first, provides good support and will not bottom out.  So if you have a high resiliency foam, with gel over that, topped by a low resiliency foam, you get a seat that feels poofy at first, then firms up as you sink in.  It's hard to know what will be right for your weight and riding position, but the most common mistake people make is to think foam is foam, and try stuffing  in more bargain foam or gel.

My suggestion to any shadetree upholsterers would be to get a variety of pure polyurethane foams (no recycled carpet pads stuff) , mostly closed cell foams, in different densities and IFDs. Layer them different ways until it feels right when you sit on it. It gives a little at first, then provides good support you have a good combo. If you can compress it down to the seat base, it will be painful in short order.  Also, make sure you vent the seat so that the air can escape when you sit down. Usually the seams will take care of this.