Ideally, you need around 16-20 shares in a portfolio to spread your risk.
I'd agree with the overall approach. A bit of commentary if I may though:
While there is a range of claims out there regarding how many shares you need to diversify. Depending on which market & timeframe the study in question was considered they got different results. On top of that the number of shares is misleading because the benefit obtained diminishes the more you buy. So *technically* any guidance would have to be linked to the fee structure used.
All of which is way too much hassle - so the Tuks lecturers suggested as a rule of thumb: ~11 you can get away with, 20 you're already wasting your time. I never actually checked up on those numbers - but the lecturer in question was rarely wrong about anything. This of course assumes you can find 11 shares you like - easier said than done.
So you are looking at R160k - R200k.
Thats assuming a very unfavourable fee structure. e.g. I pay around 1.25% for everything iirc (0.75 on buy, 0.5 on sell) - the only fixed component being the 10 bucks cap on the STRATE fee.
Crunch those numbers and it'll probably be viable to do 16 shares at say 40k instead of your 160k. [*]
More crucially though, having a portfolio that is viable at 40k means you enter the market earlier & make you early stupid mistakes before serious money is involve.
* In the interest of full disclosure I should probably add that I'm paying a fixed monthly banking fee. That as the economists would say is a irrelevant cost since I'm paying it anyway. (or was it sunk - my theory is failing me here - don't think future costs can be sunk costs

).