Fixed Vs VAN THARPE Positionsize

I need guidance from Seniors in the forum. I was comparing fixed 20% position sizing against VAN Tharpe position sizing using volatility ATR as a Stoploss and the finding is that fixed position sizing of 20% equity provides much better back-tested result (200% better that VAN Tharpe Position Size) Can you please tell me where I am doing wrong -

AFL for fixed positionsize -

SetOption( "InitialEquity", 1000000);
SetOption("FuturesMode" ,True);
SetOption("MinShares",1);
SetOption("CommissionMode",2);
SetOption("CommissionAmount",100);
SetOption("AccountMargin",100);
SetOption("RefreshWhenCompleted",True);
SetOption( "AllowPositionShrinking", True );
SetOption("MaxOpenPositions", 5);
PositionSize = -20; // invest 20% of portfolio equity in single trade
RoundLotSize = 1;

Plot( Close, "Price",colorWhite, styleCandle );

//Parameters

MALength1 = 5;
MALength2 = 20;

//Buy-Sell Logic

Buy = Cross(ema( C, MALength1 ),ema( C, MALength2 ));
Sell =Cross( ema( C, MALength2 ), ema( C, MALength1 )) ;

Buy = ExRem( Buy, Sell );
Sell = ExRem( Sell, Buy );
Short = Sell;
Cover = Buy;

PositionScore = ADX(14); // prefer stocks that have higher ADX

Plot(ema( C, MALength1 ),"5EMA",colorWhite);
Plot(ema( C, MALength2 ),"20EMA",colorBlue);

And here is with VAN Tharpe position sizing

SetOption( "InitialEquity", 1000000);
SetOption("FuturesMode" ,True);
SetOption("MinShares",1);
SetOption("CommissionMode",2);
SetOption("CommissionAmount",100);
SetOption("AccountMargin",100);
SetOption("RefreshWhenCompleted",True);
SetOption( "AllowPositionShrinking", True );
SetOption("MaxOpenPositions", 5);

Entrysignal = ValueWhen(Cross(ema( C, 5 ),ema( C, 20 )), C, 1);
Exitsignal = H-2*ATR(20);

RiskPct=1;
Stopsize = Entrysignal - Exitsignal;
SetPositionSize(100*(RiskPct/Stopsize), spsPercentOfEquity); 
RoundLotSize = 1;

Plot( Close, "Price",colorWhite, styleCandle );

//Parameters

MALength1 = 5;
MALength2 = 20;

//Buy-Sell Logic

Buy = Cross(ema( C, MALength1 ),ema( C, MALength2 ));
Sell =Cross( ema( C, MALength2 ), ema( C, MALength1 )) ;

Buy = ExRem( Buy, Sell );
Sell = ExRem( Sell, Buy );
Short = Sell;
Cover = Buy;

PositionScore = ADX(14); // prefer stocks that have higher ADX

Plot(ema( C, MALength1 ),"5EMA",colorWhite);
Plot(ema( C, MALength2 ),"20EMA",colorBlue);
Plot (Exitsignal, "Exitsignal", colorRed);

But Using VAN Tharpe position sizing CAR/MDD becomes much better than fixed psotion sizing.
If anybody gives their comments and share experience will be a great help for me

Take some time to analyze each of your trade lists, and ALL of the metrics that AmiBroker produces for you, not just CAR/MDD. In particular, see if you can find the reason for the performance differences that you have observed. For example, one common issue that leads to higher or lower CAR is higher or lower exposure, which is directly influenced by your position sizing model. When using risk-based position sizing like the Tharpe model you referenced, we expect to see more variability in the value of different positions. But if most or all of those positions are smaller than their equivalent trades using Fixed % of Equity position sizing, it may be an indication that you're taking too little risk per trade.

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