I'd be glad to see other oppinons - approach is used in very narrow players circle (one explanation is obvious - garbage )
Our pair use unlimited transfer bids combined with Raptor over 1st level suit openings (except against strong 1♣ - special defeance). Its deals well with most hands (including twosuiters) with cons of having to bid clubs at 3th level.
Schema:
Dbl and transer for two suits (exclude clubs and opened suit);
1♠ (or dbl on 1S) = T/O dbl or strong Balanced hand (after simple answer from partner new suit = 4 cards and 16-18, 2 NT=19-20 etc.)
1 NT - Raptor - 4M-5+m, outside opened suit
2 NT is good overcall with clubs, 3 clubs and above are preempts;
Cue after minor - 5-5 both majors unlimited
Cue after M - unlimited Michaels
Jump 2 M -> 6 (7 Vuln) tricks AND good 6+ suit.
We played transfer to opener's suit as 4441 t/o. It is matter of choice - for this shape "ordinary" t/o (1♠) could be used, and transfer to suit and major cue-bid could show exact twosuiter OM + lower/upper minor for example.
On opponents dbl we use pass as weak hand without fit, bid transfer with 3+ support and weak hand. Jumps are showing suit+fit, 2NT after transfer to M is good 4+ support at least to 3 level (if there is opportunity, simple cue shows same but only 3 cards support), after m is natural and invit.
Becouse of way we evaluate unbal hands (A=1.5, K=1, Q=.5 Tricks + (Fit-shortest)/2 Tricks), T/O dbl is promisisng 4+ tricks in support of non-bid suits. It make easy life of responder, who simply adds 4 to his Tricks (honors Tr. are same + (longest - shortest suit)/2) and bid to that level T/O dbler adds a level for evey trick above 4 after jump or free bid (non jump bids - 0-4 tricks are rised with 6+ Tricks 5+4=9 no need to rise).
Same about transfers - lower limit is -2/-3 (non/vul), no upper limit. Jumps are -2/-3 based on winners.
Pro's & Cons:
Pros:
- Becouse of forcing nature of transfers, it's easy to show additional strength of hand later by entering biding at later stage (even using Dbl). It solves a lot of problems with strong one or twosuiter hands, and give oportunity to describe twosuiters at low level.
Opener is on lead.
Raptor solves (almost) problem with competative hands,having 4th Major and longer minor
1♠, despite of seeming unconvenient take-out,put additional pressure in part-score batle.
2 NT (good unlimited overcall with clubs) looks too high, but it's level if you compete with goods clubs.
Simplicity of convention.
Cons:
- Opponents have oportunity to dbl transfer or step in suit as cue at low level.
It happens toplay contract from "wrong" side (it's depend...).
You waste time to explain overcalls to non clever opps.
You could play it with regular partners only.
List is not full - just some major points...