What is your 5 iron distance, and the distance of your most lofted wood? Pick the club that is easiest to hit and fill that gap. I would think the 24*.

Agree with eboos.   The 24* would be the 4 iron replacement.    You could also have a fairway wood setup of 17 and 21*.

I found the 24 much easier to hit vs the 21.  Also keep in mind that the 24 set to 23.25 would hit a fade and the 21 set to 22.5 hits a draw.

Pretty much my quandary.  I have a 26 5 iron and 4 wedges.  I have a 27H, 24H, and a 21F.  I'm going for a gap fitting to look at distance, dispersion, and comfort to sort this out.  Sets with a 25 5I would likely have 22 4I and a 19 3I,  The 21 set to 21.75 might be the best number.  The Titleist 24H and 21H correspond to the forged irons 5/4/3 at 27/24/21.

I'm pretty close to Don's setup.  I have a 19F set to 20.5, a 24* 9 wood and 27H set to 27.75.  Iron wise I have AP1 7-PW (32-36-41-46 for lofts).  I also have a nifty persimmon 34H for the gap between the 27H and 7 iron with Option B to choke down 1/2" on the 27H for lower shots.

The 21H set to 21.75 would give a small draw or close to dead straight ball flight.  You can always choke down a little to shorten the distance.  My 27H is at C3 and I hit it dead straight.  I went back to using a 9 wood after all the fuss trying to hit a 21H since last year (what I have been doing for over 2 years with success is choking down on my 7 wood and 19F for the 170-175 distance); I had a 24H but didn't have any difference in distance  vs the 27 (main point is that I can pretty much crush the 27).

You can play with adjusting the length of shafts also to adjust the distance of a club.  For instance, moving a 40" shaft from a 24 degree to a 21 degree may do the trick....this is just an example. 

This is a difficult question to answer. A fitter would really need to know a lot more about your clubs and how you hit them. What are your carry distances for your 5 iron and the club that you are trying to fill the gap between? What is your ball flight? High / Low? Do need help with carry and ball stop on the green?

These are important factors. Also getting the correct shaft for the club is just as important as the correct loft setting.

Thanks for all the replies. I carry my 5 iron 165 yds, my 24* at the 23.35* setting 175-180 well struck and my 21* at 21.75* 185 but its a little more difficult to hit. I play a stock in my 21* kaili regular and a kbs hybrid shaft in my 24* which is cut down a 1/2" from the std length due to swingweight. 

My TEE XCG3 5 wood is my money 200 yard club

I tried to put the same kbs shaft in the 21 but I couldn't hit it well for some reason. Of course the 24* head is heavier so maybe if I added a heavier weight screw in the 21 it would feel better.

I play game improvement PP-9003's and I love them. They are only a degree stronger than the AP1s except for PW and Gap I handed down to my son but I would rather not mess with the lofts on them.

IMO, it is quite frustrating for the consumer to deal with different lofts in clubs. Titleist uses old standard lofts for their hybrids but other manufacturers are using stronger lofts for the GI/SGI irons and hybrids as well.

I guess long story short, experiment and/or get fitted for the hybrids

Greg