I ran across a spanish 21 bj promotion that paid 2-1 for suited blackjacks and 3-1 for blackjack in clubs. I realized I didn't know what the edge was for spanish 21. I just used my memorized solution for regular blackjack. I later calculated the correct edge for spanish 21, which is below.
6Deck: (24/288 x 72/287) + (72/288 x 24/287) =

3456/82656 = 4.18118% probability of BJ.

4.18118%/4 = 1.04529% probability of suited BJ.

4.18118%/16= 0.26132% probability of clubs BJ.

4.18118% x .5 = 2.09059% BJ 2-1 extra edge.

1.04529% x .5 = .52264% BJ suited 2-1 extra edge.

.26132% x 1.5 = .39198% BJ clubs 3-1 extra edge.

(.26132% x 3 x.5) + (.26132% x 1.5) = .78396% extra

edge for above promotion. .78396% -.42% = +0.36396% off the top edge for 6D,H17,DDD,2-1 BJ suited,3-1 BJ clubs.

100/4.18118 = blackjack every 23.91669 hands.

8Deck32/384 x 96/383) + (96/384 x 32/383) =

6144/147072 = 4.17754% probability of BJ.

4.17754%/4 = 1.044385% probability of suited BJ.

4.17754%/16 = .261096% probability of clubs BJ.

4.17754% x .5 = 2.08877% BJ 2-1 extra edge.

1.044385% x .5 = .5221925% BJ suited 2-1 extra edge.

.261096% x 1.5 = .3916443% BJ clubs 3-1 extra edge.

100/4.17754 = blackjack every 23.93753 hands.