Brief:
Used 24mm motor mount, ya bilge rat, reinforced fin joint w/fiberglass.

Modifications:
Seein' that Quest Icarus uses 18mm motor mount, and has a payload section, I think a A/B/C motor would nay have enough power t' give this an impressive flight if a payload were used, so I decided t' give this rocket a little boost.

I added a 24mm tube instead o' a 18mm, matey, arrr, because now I have opened up this rocket t' t' power o' D/E/F and possibly G. Blimey! T' centerin' rings were designed for a 18mm motor, so therefore I took a trusty old xacto knife, and cut it to fit a 24mm tube. It's really nay that hard, me hearties, just take a 24mm tube, me hearties, ya bilge rat, trace around it with a pencil, shiver me timbers, and cut INSIDE t' line. Well, blow me down! Avast! just keep cutting/sandin' until the 24mm tube fits. Ya scallywag! Arrr! Use epoxy t' attach t' centerin' ring, ya bilge rat, because you want t' be able t' allow t' rocket t' take t' kick o' a G motor.

Then I went t' attachin' t' fins. Begad! Blimey! Blimey! Blimey! I've used epoxy t' attach t' fins because G motor exerts a lot o' thrust, and I hate seein' t' rocket with broken fins. Begad! Blimey! Blimey! Blimey! Blimey! Blimey! So if you want, matey, me bucko, ya bilge rat, take some fiberglass cloth, shiver me timbers, cut into tapes, and epoxy them t' t' joints, so after it cures, me hearties, arrr, me hearties, t' joint will nay move at all.

Finishing:
After t' modification with fiberglass fin joint reinforcement, t' finishing becomes a pain. Blimey! Blimey! Begad! Blimey! Since t' epoxy seems t' be hard t' sand, matey, me bucko, I have t' keep sandin' tirelessly and achievin' little result. Avast! Blimey! Arrr! Blimey! I went t' constantly applying primers (and it keeps wrinkling!) then painting, me hearties, but after a long work, me bucko, it paid off, and you can't tell t' joints has been reinforced (that is until you try to break t' fin joints that is)

Flight:
Motors: After this modification, t' model will become heavier, me hearties, so use motors with low delays, ya bilge rat, such as a A8-3 and B6-2 and so on, me hearties, DO NOT use upper stage motors, me hearties, because I made that mistake and t' rocket pranged! First flight I used A8-3 and it be perfect, arrr, but t' second flight I used a B6-6 and it didn't eject until it was 3 inches into t' ground!!!

Summary:
Quest makes okay rockets (better than Estes) but they don't have 24mm....