Source: www.vba.asn.au 
The standard responses to 0314 RKCB are as follows:
| 4 |
4NT | Assume are trumps |
| 5 |
0-3 | |
| 5 |
1-4 | |
| 5 |
2 (or 5) without Q |
|
| 5 |
2 (or 5) with Q |
|
After 5 or 5, a step bid is then used as a trump queen ask. The standard responses to these are:
| 4 |
4NT | Assume are trumps |
| 5 |
5 |
5=Asks for Q |
| 5 |
No Q |
|
| 5NT | ? I don’t know what’s «standard» | |
| 6 |
Q with K |
|
| 6 |
Q with K |
|
| 6 |
Q with K |
|
| 6 |
Q with no Kings |
|
There are two major problems with this:
(1) 5NT is not utilised.
(2) If opener bids 6 with Q and no other Kings, how can responder investigate a potential grand if responder wanted to ask about 3rd round controls (such as a vital Queen in a side suit, or maybe a doubleton)?
I am uncertain as to why 6 is taught as the bid to show the Q with no side kings because it doesn’t make much sense to destroy so much bidding space when responder could be looking for a grand even without the aid of other kings.
A much better improvement would be to use the 5NT bid as the «Q with no other Kings» so responder still has all of the 6-level bidding to investigate third round controls. No doubt this is not the «best» version of RKCB available but it is certainly a better improvement than what the standard/default responses are.