Review the prior article for the description of the main idea.
When responder's suit is spades, it is necessary to cater for the possibility that he has a weak major two-suiter and wants to offer a choice of contracts at the 2-level. Transfers are still great for doing that.
1 minor - 1 Spade
1NT - ?
2 Clubs - forces 2 Diamonds, to pass or invite. Not described in this article. Check earlier articles for more info.
2 Diamonds - Transfer to hearts. May be weak.
2 Hearts - Transfer to spades. Either a weak one-suiter or a GF hand.
2 Spades - NF, 5 spades and 4-card support for opener's minor. This deals well with the dreadful possibility of opener having a singleton in spades.
2NT and beyond - as in XYZ
When responder shows hearts, opener must show preference by bidding either 2 Hearts or 2 Spades. Now, any further move by responder shows a GF hand. (Note that responder never has an invitational hand -- he would have begun with 2 Clubs). Responder bids naturally, using 2NT very often as a waiting bid.
After a transfer to spades, the structure is very similar to the one presented in the last article:
1 minor - 1 Spade
1NT - 2 Hearts
2 Spades - ?
2NT: Transfer to clubs. Does not guarantee 5 spades. Opener confirms 4 cards in clubs by completing the transfer, and bids something else without 4 clubs.
3 Clubs: Transfer to diamonds. Same idea.
Responder denies hearts when he skips over a 2 Diamond rebid, and so the next 3 bids show spade one-suiters.
3 Diamonds: A nice 5-card spade suit (will play well opposite Hx) in a balanced hand.
3 Hearts: slamish one-suiter, looking for support (3 cards or Hx)
3 Spades: slamish one-suiter, does not need support (something like KQJ9xx, presuming a doubleton with partner).
Jumps to the 4-level show voids (immediate jumps, over 1NT, show singletons).
I have played this structure for years. It is simple and easy to remember. It becomes even more efficient if you show your balanced hands via a relay after a 1 minor opening. In this case, 1 of a major followed by GF action shows an unbalanced hand, ergo, 5 cards there. You don't have to be concerned about strong balanced hands, and this simplifies the bidding.
One adjunct that really helps with accurate bidding is using the sequence 1m-1M-1NT-2C-2D-3NT (an impossible bid in "classic XYZ") to show a choice of games in a 5332 hand (or something similar -- perhaps 5422 with good doubletons). It will also help with slam bidding if you take this possibility out of the way.